Kyle Hendricks, Ace

 Kyle Hendricks has been really good this year.  You don't need me to tell you that.  But, I am going to tell you about it anyway.  What is to follow is the first in a two-part series about Kyle Hendricks' incredible season.  This article will focus on why Hendricks is so good this year.  My next article will explain how he's been able to pitch so well.

Hendricks has a 2.17 ERA and has already won 11 games -- a career high.  Right now, it's hard to imagine where the Cubs would be without Hendricks in the rotation.  Yet, Hendricks entered Spring Training fighting for a spot in the rotation with Adam Warren, who isn't even in the Cubs' organization anymore.  The Cubs returned the reigning NL Cy Young winner, a guy that signed a $155 million contract the year before, a newly-signed free agent who is the only pitcher to ever win the clinching game of a World Series for two different franchises, and another solid veteran who has now had three consecutive seasons with double digit wins and an ERA under 4.  Three of these veteran starters currently have an ERA under 3 and the other is at 3.56.  And, despite all of that, Kyle Hendricks has been the most dependable starter on the staff.

While the rest of his rotation mates completely unraveled in July, Hendricks was unflappable.  Of all pitchers that pitched at least 20 innings in July, Hendricks posted the lowest ERA in baseball.  As his rotation mates have returned to form, one would be remiss to not accept Hendricks falling back to Earth a little.  Alas, he followed up his incredible July by being named the NL Player of the Week in the first week of August.  Hendricks had to share the award with some guy who hit his 3,000th career hit.  Maybe if he hadn't given up that one run in his 16.1 innings of work, then Ichiro would have had to settle for second place.

Hendricks' start on August 1 probably would have been viewed as the best start of any Cubs pitcher this year, if not for that no-hitter that Jake Arrieta pitched earlier in the year.  The night before, to close out July, the Cubs trotted out Brian Matusz for a spot start.  Matusz lasted all of three wretched innings before giving way to the bullpen.  That game would end up lasting 12 innings before the Cubs pulled out an exhilarating come-from-behind victory.  The bullpen was left depleted.  They'd just pitched 9 flawless innings.  And the Cubs hadn't had an off day since July 21.  Regardless, the Cubs had a game to play the next day.  I'm sure Joe Maddon told Hendricks that he needed him to pitch well and to pitch deep into the game.  "No problem, skip.  How about a complete game shutout," responded Hendricks, stone-faced.

The Cubs still haven't lost since that game.  And Hendricks has inserted his name into the NL Cy Young conversation.  Seriously.  He could win the Cy Young this year.  He's not the favorite or anything.  But, his name is in the discussion.  He's at least one of the top 10 or so most-deserving candidates.  And with Clayton Kershaw's season possibly being over, there isn't really a unanimous favorite right now.  Back in May, before I had started blogging here, I made a post on the northsidebaseball.com forums discussing some things I'd seen in Hendricks that looked very encouraging.  At the time, Hendricks was sitting with a 2-3 record and a 3.51 ERA, having not completed a full 7 innings in any start.  Still, I wondered in the post if Hendricks might be on the verge of "some Dallas Keuchel-type shit."

Keuchel, like Hendricks, is a soft-tossing pitcher that relies on location and deception while inducing a lot of weak contact.  Keuchel has since fallen apart.  But, at the time, he was coming off of a season in which he won the AL Cy Young.  And I wondered if Hendricks might be able to replicate that type of success.  In the end, I surmised that, no, Kyle Hendricks was not going to match Dallas Keuchel's 2015 season.  You'll have to forgive the naiveté of the three-month-younger version of myself.  Hendricks absolutely is on some Dallas Keuchel-type shit.

There are a number of reasons why Kyle Hendricks is all of a sudden one of the best pitchers in baseball.  I'm just going to rattle off some of the ways he rates among the best in baseball.

Of qualified starters, Hendricks ranks 2nd in MLB in ERA.  He ranks 14th in FIP.  He ranks 29th in xFIP.  He ranks 11th in HR/FB.  He ranks 10th in HR/9.  He ranks 15th in GB%.  He ranks 7th in WHIP.  He ranks 10th in batting average against.  He ranks 9th in OBP against.  He ranks 3rd in slugging % against.  His first-pitch strike % ranks 3rd.  He ranks in the top 40 in BB/9, K-BB%, and K/BB.  He's been efficient, with his average pitches per inning ranking 16th.  According to Fangraphs' batted-ball data, his hard-hit % is the third-lowest.  His soft-hit % is the highest in the majors.  His WPA (win probability added) ranks 5th.  His "clutch" score is 23rd.  His average Game Score ranks 13th.  He ranks 19th in fWAR.  He ranks 8th in RA9-WAR.

However you slice it, Kyle Hendricks has pitched very well this year.  (For what it's worth, he's also fielded his position well, ranking among the top pitchers defensively, with a couple defensive runs saved.)  There is one thing that Hendricks isn't so great at.  He doesn't strike out very many guys.  His 7.58 K/9 is actually below the league average of 7.70 for major league starting pitchers.  Of the 22 other pitchers that also rank in the top 30 in the majors in both ERA and FIP, only 5 -- Aaron Sanchez, Tanner Roark, Steven Wright, Masahiro Tanaka, and Rick Porcello -- also carry with them below average rates in K/9.

To be fair, K/9 isn't the best measure to look at if we want to know how adept a pitcher is at striking guys out.  Since Hendricks doesn't allow very many base runners, he isn't facing as many batters per inning as a lot of other pitchers.  If we look at it on a per batter basis, instead of a per inning basis, Hendricks rates better.  His 21.2% K% ranks 40th among qualified starters and is well above the league average of 20.1% for starting pitchers.  His K% might also be just a little low for what you would expect based off of his underlying numbers.  Mike Podhorzer developed an expected K% that is able to account for about 90% of a pitcher's K% -- the other 10% essentially being due to luck from sequencing.  You can see his formula in this article at Fangraphs.  Using his formula, Hendricks' xK% is 21.6%.  So, if we strip away sequencing luck, we'd expect Hendricks to pick up a few more strikeouts than he's actually accrued.

I mention his K/9 rate, though, because I want to point out how much more reliant Hendricks is on getting outs on balls in play compared to other top pitchers.  Jose Fernandez doesn't have to worry as much about getting outs on balls in play because so many of his outs come via the strikeout.  With more balls in play, Hendricks has to hope they don't do much damage.  Ah, but that's where Hendricks really excels.

Mike Petriello wrote a really good article about this at mlb.com recently.  I would urge everyone to read it.  For one, Petriello does a great job of describing how good Hendricks is at inducing weak contact.  And as long as everyone agrees to read it, then I won't have to repeat all of the same things that he mentions.  If you're too lazy to click through, though, here are the cliffs:  Hendricks is quite adept at inducing ground balls.  Ground balls don't do much damage, so that's certainly a good start.  On the balls that often do damage, though -- the ones in the air -- Hendricks also fares quite well.  Of the 139 pitchers who have thrown at least 1,250 pitches this year, Hendricks has the lowest average exit velocity on balls hit at a vertical launch angle between 20° and 50°.  94% of all home runs come in this range.  And Kyle Hendricks' average exit velocity in this range is over a full mile per hour lower than any other major league starting pitcher.  I wrote a lot about this stuff in my article earlier in the year examining the Cubs' ability as a team to induce weak contact.  Kyle Hendricks is one of the main reasons the team, as a whole, is so successful in this regard.

On all balls in play, Hendricks ranks 7th among those same 139 pitcher in terms of lowest average exit velocity.  Tony Blengino developed an algorithm to find an "Adjusted Contact Score."  He'll post updates on his data periodically at Fangraphs.  Essentially, he uses all batted ball data, breaking things into categories, to find out how effective pitchers are at limiting production on balls in play.  In his last update in June, Hendricks ranked first in the National League.  Kyle Hendricks is elite when it comes to contact management.  That much we know.  But what does this mean?

Well, we know that exit velocity is very important for hitters.  It correlates strongly with offensive production.

http://cdn.fangraphs.com/blogs/wp-content/uploads/2016/02/EXIT-VELOCITY-AND-wOBA-IN-2015-1.png 

It's very important to pitchers, alike.  The starting pitchers with the three lowest average exit velocity measures last year were Jake Arrieta, Clayton Kershaw, and Dallas Keuchel.  Two of those three were your Cy Young winners last year and the other is Clayton Freaking Kershaw.  That's neat to know.  But does it mean anything?  We already knew those guys were good.  Clayton Kershaw is good at everything; of course he is good at this.  For this information to be useful it needs to be able to provide us information that we didn't already know -- information we can then use to better our understanding of how pitchers perform.

The best tool we have to measure a pitcher's performance right now is probably FIP, which stands for fielding independent pitching.  Not only is it a better measure than ERA, but it is scaled to match ERA -- the league average FIP will always equal the league average ERA.  FIP is easy to understand.  And it's become ensconced in baseball vernacular.  For the uninitiated:  FIP only concerns itself with home runs, walks, hit by pitches, and strikeouts.  FIP is the progeny of DIPs theory.  If you aren't up-to-date on DIPs theory, I don't have the time to get you caught up.  There have been decades of research on DIPs theory.  And there is too much for us to go over.

I'll try to be concise in explaining the premise, though.  The idea behind DIPs theory is that a pitcher can't control what happens when a ball is put in play.  There's too much noise:  defensive ability, defensive positioning, luck, the list goes on.  ERA is a bad measure because it doesn't take into account these factors, among other things such as sequencing luck (in what order you allow base runners).  DIPs theory is generally accepted to be true.  FIP works... with most players.  There are some players that consistently run ERAs lower than their FIPs.  These pitchers are often elite pitchers, such as prime Greg Maddux.  We've also found that FIP doesn't do a great job of accurately measuring extreme fly ball pitchers, such as Chris Young.  As such, SIERA was created in order to account for certain ball-in-play intricacies.  SIERA is better at measuring the guys that stick out like a sore thumb, like Chris Young.

But, there are still other pitchers who seemingly randomly outperform their FIP, such as, say, Wei-Yin Chen (until this year, that is) or Johnny Cueto.  Johnny Cueto is an interesting case.  He's a really good pitcher.  He's not exactly Clayton Kershaw, though.  And yet, he's found a way to post a lower ERA than his FIP in all nine years he's been in the big leagues, sometimes by significant margins.  His career ERA is nearly half a run lower than his career FIP.  And there's nothing about his batted-ball profile that is all too strange.  He generally rates well in metrics like soft- and hard-hit %, but not so well that we would expect him to magically beat FIP.  He's right in line with the league average fly ball rate for his career.  And his fly ball rate fluctuates quite a bit year-to-year.  And, yet, it doesn't matter too much where his fly ball rate falls, he still manages to surpass his FIP.  This isn't Chris Young, with his crazy high fly ball rate.  There's seemingly no explanation to it.  At least not yet.

There is one possible explanation.  It could be a fluke.  In a normal distribution, we'd expect half of the pitchers each year to post a FIP lower than their ERA and half to post a FIP higher than their ERA.  As such, we'd expect a few pitchers to fall in the same category for a long stretch.  We don't know which ones will do this.  But, someone's likely to do it.  That's where it gets hard to separate the true FIP overachievers from the lucky souls.  Johnny Cueto seems like a safe bet to be the real deal, though.  He isn't just beating his FIP; he is beating his FIP by an incredible amount time and again.  That's different than simply beating it by a little bit for five or six years consecutively.  It's much less likely that he is randomly on the fringes of our distributions year after year.  If you flip a coin enough times, you are going to land on heads seven or eight times in a row.  You're probably not going to land it on its edge nine times in a row, though. 

Where am I going with this?  Well, I think Kyle Hendricks is a FIP beater.  At least this iteration of Kyle Hendricks is.  I'll try to prove it, but you are within your rights to call me on it.  I can't actually prove it.  I'm not smart enough to do that.  But there are people much smarter than me that might be able to prove it, now that we have some more information at our disposal.

Let's see how we can prove it, based on what we know already.  Well, Hendricks isn't an extreme fly ball pitcher like Chris Young.  Quite the opposite, in fact.  There is one thing that Hendricks does that other ground ball pitchers don't, though.  Hendricks runs a very high infield fly ball rate.  Since he entered the league in 2014, there are only three pitchers that have maintained a ground ball rate over 50% and an infield fly ball % over 11%.  Their names are Kyle Hendricks, Clayton Kershaw, and Dallas Keuchel.  Pitchers that get a lot of pop ups are able to outperform their FIPs.  However, it's much easier for fly ball pitchers to get pop ups.  This makes sense intuitively.  Think of why pitchers get pop ups.  It's because of how they pitch the ball.  Most extreme fly ball pitchers pitch like Chris Young does.  Young throws high fastballs with good spin on them.  These are more likely to be popped up than the sinkers coming from Brad Ziegler.  Of pitchers with at least 800 innings pitched in the last ten years, guess who has the highest infield fly ball % in the majors.  Chris Young, of course.  By a lot.

So that's one way for Kyle Hendricks to outperform his FIP.  Clayton Kershaw is the only ground ball pitcher that gets as many pop ups as Hendricks.  And pop ups are converted into outs nearly 100% of the time.  For their part, Fangraphs counts pop ups the same as strikeouts when computing fWAR.  The result is the same.  This is something that won't show up in FIP.  And this is one of the main reasons why extreme fly ball pitchers are able to outperform FIP.

What's another way that Hendricks can beat FIP?  Well, FIP assumes that each pitcher will have a league average BABIP.  One way to suppress BABIP is by suppressing exit velocity.  As we've already seen, Hendricks does a magnificent job of suppressing exit velocity.  This is the major flaw of FIP and DIPs.  It presupposes that a pitcher has no control of balls in play.  That's simply not true.  In the article that I just linked, Rob Arthur shows that hitters do have more control over the exit velocity of a batted ball -- five times as much, in fact.  But, the top pitchers are able to suppress exit velocity by as much as 1.5 miles per hour.  That much loss in exit velocity can have a significant impact on BABIP.

As such, might we consider that pitchers with lower exit velocities are be able to beat their FIPs?  Craig Edwards at Fangraphs ran a study last year trying to find meaning in exit velocity for pitchers.  The results suggested that, well, not so much.  He split pitchers into three groups by average exit velocity.  The top third performed much better than the middle third.  The middle third, in turn, performed much better than the lowest third.  But, exit velocity actually had a higher correlation to FIP than ERA.  Essentially, what happened is that the pitchers in the top third were simply good pitchers.  The benefits from their lowered exit velocities were already accounted for in FIP.  Pitchers that were able to suppress exit velocity also were able to suppress home runs, and they struck out more batters.  This makes sense.  Guys that are difficult to square up are probably difficult to make contact against, in general.  And, obviously, they will be difficult to homer against.  The components of FIP, unknowingly, were tracking this skill already.

The main benefit of suppressing exit velocity, according to Edwards was in suppressing home runs.  This is something that we can use.  xFIP assumes that a pitcher will have the league average HR/FB rate.  Hendricks (and others that suppress exit velocity) aren't going to have league average HR/FB rates.  This is why his FIP is lower than his xFIP.  xFIP isn't going to be a good measure for a guy like Hendricks.

But, still, I am wont to question these findings, at least partially.  We already know that FIP works for the vast majority of pitchers.  There are but a few outliers.  So we shouldn't expect to find a significant correlation between exit velocity and an ability to beat FIP.  We already knew that FIP was a good measure.  So if there was a significant correlation between exit velocity and production not measured in FIP, then FIP wouldn't be a good measure.  FIP wouldn't work very well if DIPs theory wasn't mostly true.

What we are looking for are ways to identify the outliers, though.  I wonder if the elite exit velocity suppressors might be able to beat their FIPs.  I'm talking about the truly elite.  Jake Arrieta and Dallas Keuchel were able to win Cy Young awards last year while maintaining elite exit velocity readings and outperforming their FIPs by significant amounts.  By splitting the groups into thirds, a guy like Hendricks, who is elite at suppressing exit velocity, is lumped in with a bunch of guys that are closer to the middle of the pack.  If, say, the outliers are mainly on the margins, then the data on guys in the 30th percentile aren't as pertinent as the data on other 1 percenters.

And the findings of Arthur and Edwards are at odds, anyway.  If certain pitchers are able suppress exit velocity to an extent, and if exit velocity correlates to BABIP, then we should expect there to be a correlation between exit velocity and an ability to beat FIP.  Again, FIP presupposes a league average BABIP.  If exit velocity suppression is a skill, then those that can suppress exit velocity -- and, in effect, BABIP -- should outperform FIP. 

The bottom line is that we don't have enough data on exit velocity to draw any conclusions.  I'm inclined to believe that Arthur's findings have some merit.  But, we don't have any concrete answers.  If anything, even given exit velocity measurements, we should still trust FIP more than ERA.  ERA is simply a bad stat.  And we never should expect it to correlate more strongly than FIP to anything, including exit velocity.  There's just too much noise in ERA.

So, if we are left at a crossroads concerning exit velocity and FIP, let's head back to where we started:  Extreme fly ball pitchers.  I showed that Hendricks was able to induce a lot of pop ups.  And fly ball pitchers can outperform FIP, in part, because of pop ups.  But, that's not the only reason why extreme fly ball pitchers beat FIP.  Fly ball pitchers, generally, run lower BABIPs on all fly balls than ground ball pitchers do.  The inverse is true with ground balls.  Ground ball pitchers run lower BABIPs on ground balls.    The effects are more pronounced when pitchers take things to the extreme.  There is more to be gained in BABIP suppression by going from 55% to 60% in ground-ball rate than by going from 50% to 55%.  SIERA accounts for these effects.

The effect isn't as pronounced with ground ball pitchers, though.  Take Brandon Webb, for instance.  He carried a very high ground ball rate.  And he consistently outperformed his FIP.  But he didn't outperform it quite like Chris Young does.  I think it's pretty obvious why.  A ground ball is a ground ball.  It isn't going to do too much damage even if it isn't fielded.  If a fly ball isn't caught, then it's probably dropping in for extra bases.  So turning more fly balls into outs is more beneficial than turning more ground balls into outs.

And how does Chris Young turn more fly balls into outs?  Well, for the same reason that he generates a lot of pop outs:  That's what his pitches are meant to do.  Fly ball pitchers get more hang time on their fly balls.  Fly balls hit off of fly ball pitchers are hit at higher trajectories.  Accordingly, outfielders have more time to get under their fly balls.  There has been a lot of research on how different types of contact correlate to BABIP.  Take this snippet from the article I just linked from Mike Fast at Baseball Prospectus, explaining why ground ball pitchers give up more hits on fly balls.

That's where we need to look.  Exit velocity didn't give us a definitive answer.  Maybe launch angle can help us.  Let's head over to Baseball Savant to see how Hendricks compares to other ground ball pitchers when looking at launch angle.  I am going to search for all pitchers that have thrown at least 1,250 pitches this season.  This leaves 139 pitchers -- basically all qualified starters and then a smattering that come up just short of qualification.   Then, I am going to filter out all ground balls.  I'm then going to compile a list of the top 20 qualified starters in terms of ground ball rate.  And we'll go through the results.  

The first two columns are going to show these 20 pitchers and where they rank in terms of ground ball rate.  The third column is going to show each pitcher's rank, out of the 139 total pitchers, in terms of highest average vertical launch angle on non-ground balls.  The fourth column will show their rank in terms of lowest BABIP on these batted balls.  The fifth will show ranks in terms of lowest average exit velocity on these batted balls.  And the last column will show ranks on slugging % on these batted balls.  We're most concerned with the third and fourth columns, showing launch angle and BABIP rankings.

(I did this research a few days ago, so it's not up-to-date.  If you'd like to look for yourself, here is a link to the updated data for launch angle.  And you can change the "sort by" feature to find the data in the other columns.)

Well, what do we have here?  Nearly all of these pitchers are in the bottom 25% of the league in terms of launch angle on balls in the air.  It follows what we read above.  Ground ball pitchers, generally, give up fly balls at lower launch angles than fly ball pitchers.  And they also have really poor BABIPs on these balls, because these types of balls are more often line drives, whereas fly ball pitchers are collecting more lazy fly outs on these balls.

18 of these pitchers rank in the bottom 51 pitchers in terms of launch angle.  There are two exceptions:  Jake Arrieta and Kyle Hendricks, who both sit comfortably above league average.  Hendricks, in fact, is well above league average.  Hendricks is even above some guys with heavy fly ball repertoires, like Stephen Strasburg and Matt Shoemaker, who both rate in the top 20 in the league in terms of fly ball rate.

If you look at the top of the list, you'll see extreme fly ball pitchers like Marco Estrada, Justin Verlander, and Matt Moore.  You'll also notice that a lot of the guys near the top of the list are guys that are currently outperforming their FIPs.  Take Marco Estrada, for instance.  Estrada ranks 7th in MLB in terms of the largest negative difference between ERA and FIP.  He ranks 5th in terms of fly ball %.  He ranks 1st in terms of infield fly ball %.  And he ranks 1st on this list of average vertical launch angle on balls in the air.  Outside of fly ball %, these are all things that Kyle Hendricks does well, too.

This data isn't skewed by all of those pop ups Hendricks induces, either.  To remove those infield flies out of our data set, we'll search for average vertical launch angle on all balls hit at least 150 feet and with a launch angle over 0°.  Hendricks has the 27th highest launch angle on these flies into the outfield.  He isn't supposed to be able to do these things well.  He defies everything we know about ground ball pitchers.  (So does Jake Arrieta.  An embarrassment of riches, I tell you.)

I've also included exit velocity and slugging percentages in that table, too.  You'll notice something here.  While most of these ground ball pitchers also struggle with suppressing exit velocity on these batted balls, some have shown an ability to post low exit velocity numbers.  These guys mostly are the guys that do better according to launch angle, as well.  But the important thing is this:  Despite mostly pedestrian BABIP numbers, they are able to run low slugging percentages if they can suppress exit velocity.  This seems to help confirm the data we saw in the Fangraphs piece by Craig Edwards earlier.  Suppressing exit velocity mainly benefits a pitcher by suppressing home run rate.  These pitchers with good marks in exit velocity on these batted balls are able to limit slugging by limiting homers. BABIP is more a function of launch angle, while slugging is more a function of exit velocity.

Let's look at the top four guys on this list in terms of highest vertical launch angle:  Hendricks, Arrieta, Chatwood, Martinez.  They also have four of the six lowest BABIPs on this list.  And they have the four lowest exit velocities on this list.  You'll notice something when you look at their stats.  They all have FIPs that are markedly lower than their xFIPs, because they are able to suppress their home run rates.  And they all have ERAs markedly lower than their FIPs, because they are able to suppress their BABIPs by getting balls in the air at higher trajectories.  (Tanner Roark also falls in line with these four in these batted-ball aspects.  He's also a FIP beater and an xFIP beater.  He just moved into 20th in terms of ground ball rate, but after I had compiled this data, though.  So he wasn't included.)

This is what we were looking for.  This is how you beat FIP as a ground ball pitcher.  These guys get weak contact in the form of ground balls.  And they also get weak contact on balls hit in the air.  And Hendricks is better than anyone at it.  He is leaps and bounds better than other ground ball pitchers at getting fly balls at high trajectories.  And his average exit velocity on balls in the air is the lowest of any pitcher in the league.  Practically everything hit off of Hendricks could be qualified as weak contact.

While we're here, let's check out this data on ground balls.  We'll look at the same list, with the same parameters, except we are going to look at only ground balls.  The columns are going to show ranks for lowest vertical launch angle, lowest BABIP, and lowest average exit velocity.

As you can see, nearly all of these guys rank in the upper half of the league in terms of launch angle and BABIP.  But, it's not as pronounced as we saw with balls in the air.  These guys, generally, aren't the elite of the elite, as fly ball pitchers are on fly balls.  They are good, sure, but not so much that we would consider any of this data to be extremely significant.  This might explain why ground ball pitchers don't outperform their FIPs as often as fly ball pitchers.  They don't get as much benefit from doing what they do best.

You'll notice the two guys that do have elite BABIPs on ground balls are Arrieta and Hendricks.  I'm afraid they have Addison Russell and Javier Baez to thank for most of this.

Why don't ground ball pitchers receive as much of a boost on their ground balls?  Well, I think it has a lot to do with the differences in ground balls and fly balls.  On ground balls, there is too much other noise going on.  Harder hit fly balls go farther, and ones with less hang time drop faster.  A ground ball is a ground ball.  There are things more important than launch angle and exit velocity when we examine ground balls.  For instance, the speed of the hitter matters on ground balls, unlike on fly balls.

Look at that chart, though.  A 40-mph ground ball has nearly the same expected value added as a 90-mph ground ball.  The same is true for 50-mph and 80-mph.  Sometimes slow rollers are better than harder hit balls that are routine ground outs.  And defensive positioning is very important.  Is there a shift on?  Is a runner being held on?  Are the infielders playing in?  Or at double play depth?  And, mainly, defensive ability matters a lot more.  That's why we see the best defenders in the middle of the infield and lumbering sluggers are often hidden in corner outfield spots.

There's just too much noise.  The most you can ask of your ground ball pitcher is that he gets a ground ball.  If he does that, the rest is out of his control.  This is why DIPs theory exists.  When we complain about our pitchers getting "BABIP'd to death," what are we complaining about?  Mostly we complain when stupid ground balls find holes or stupidly die in front of an infielder.  Or when Billy Hamilton stupidly beats out a routine grounder.  Ground balls are stupid and unpredictable.

They are usually a pitcher's best friend, though.  And that's because, even when a stupid one goes for a hit, it is usually just a single.  When a fly ball drops in, it's often for extra bases.  Let's look at it this way.  The league average slugging % on ground balls hit under 100 mph is .235.  The league average slugging % on ground balls hit at least 100 mph is .469.  There's definitely a difference.  But, I'd still rather my pitcher give up a ground ball, even if it is smoked.  The league average slugging % on non-ground balls hit under 100 mph is .496.  The league average slugging % on non-ground balls hit at least 100 mph is 1.863.  Exit velocity matters a lot more on balls hit in the air.

If you are skilled at suppressing production on balls in the air, you are much more likely to beat your FIP than if you are skilled at suppressing production on ground balls.  That doesn't mean that you can't beat FIP by limiting ground ball production.  It only means that the gains will be negligible.  And Hendricks fared well on ground balls in the table above.  But, as we saw above, exit velocity doesn't matter quite as much on ground balls.  Zach Britton gets more ground balls than anyone.  And he has the 348th lowest average exit velocity on ground balls of the 370 pitchers that have thrown at least 500 pitches this year.  He also has the 8th lowest BABIP of those same pitchers.

So raw exit velocity data isn't going to give us much.  We need to find the specific types of ground balls that are most likely to do damage.  Let's inspect this image from the 538 article I linked earlier.

You start seeing some orange when you get into ground balls hit at least 90 mph and at vertical launch angles between 0° and 10°.  I wrote about these types of ground balls in my article from earlier this year about Addison Russell's defense.  (Spoiler alert:  Addison is proficient at turning these balls into outs.)  These types of balls are, well, hit hard.  But, more importantly, they are hit on a low line.  They are the types of balls that often require a diving snag, or they might take a tricky hop right before they get to an infielder.  They require highlight reel plays by infielders.  More often, they eat the infielder up, or the infielder never stands a chance at them.

If you hit a ball really hard, but at a lower launch angle, then those balls turn into sharp five-hoppers or hard rollers.  These balls are rather easy to play.  They get out to the infielder.  But they lose steam the whole time.  It's the ones that are still coming in hot when they get out to the infielder that are hard to handle.

Balls hit at least 90 mph and at vertical launch angles between 0° and 10° have a BABIP of .598 league-wide.  You'll also see in the above image that the orange starts drifting down on the launch angle side a little once exit velocity reaches 100 mph.  So we'll also search for balls hit at least 100 mph and at vertical launch angles between -10° and 10°.  These balls have a BABIP of .539 league wide.  These are the types of ground balls that are best to be avoided.  The other ones don't matter as much.  There's too much randomness involved in those balls.  And, on the whole, they are mostly routine plays for infielders.

Let's go back to our list of ground ball pitchers from before and see if any of them are able to limit the amount of these types of batted balls hit off of them.  This would be a good way to lower your BABIP.  We're going to sort those same 139 pitchers as before, this time by the lowest % of pitches thrown that produce these types of batted balls.  We would expect the ground ball pitchers to appear at the bottom of the list.  It's sorted by total pitches thrown and not by ground ball %.  Since the ground ball pitchers give up more ground balls in total, it would seem to follow that they would give up more hard-hit ground balls.  (If you care to look, here is the link to the third column and here is the link to the fourth column.

What do you know!?  Kyle Hendricks and Jake Arrieta are the only two pitchers on this list that have been able to avoid these types of hard-hit ground balls.  Again, Kyle Hendricks is leaps and bounds better than his fellow ground ball pitchers in this regard.  Despite getting more ground balls than 85% of the starting pitchers in baseball, he is somehow able to give up fewer dangerously-hit ground balls than all but a few pitchers.  We've now learned that Hendricks is better than all of his peers at getting weak contact on both fly balls and ground balls.

I've written extensively in the past about the work that Andrew Perpetua has been doing this year.  Here is a primer.  Mr. Perpetua is using Statcast data to figure out expected offensive production.  Essentially, he is taking batted ball types -- measuring exit velocity, and vertical and horizontal launch angles -- and dropping them into buckets.  When a ball is put in play, you can look at all similarly hit balls and figure out an expected value.  The outcome of a particular ball in play doesn't matter; the only thing that matters is what usually happens when a ball is hit in similar fashion.  This will remove a lot of noise from ball-in-play data.  It's not perfect, but I believe it to be where we need to head with all of this new Statcast data we have at our disposal.

Perpetua is continually updating this information at xstats.org.  wOBA is one of the best stats we have to measure offense.  Perpetua keeps an xOBA stat, tracking what we should expect a pitcher's wOBA against to be.  This will basically do the same thing as FIP, except it will incorporate expected batted ball outcomes, instead of assuming league average results.  Of pitchers with 100 innings pitched, Kyle Hendricks ranks 4th in xOBA.  Only Clayton Kershaw, Max Scherzer, and Jose Fernandez have lower xOBAs than Hendricks.

I think it's pretty obvious that Kyle Hendricks is better than his FIP would indicate.  And, even still, if you don't believe anything I've written (in which case, if you are still around, I salute you), he still has been really good, assuming this batted-ball data is hogwash.  He ranks 14th in the majors in FIP among qualified starters.  So when I see something like this, then I get confused:

That's from a Keith Law chat earlier this week.  Well, Keith, yes, he has been helped by his defense.  He has the best defense in the league behind him.  But, depending on your definition of a "#1," he's still pretty close if we assume league average results on balls in play.  And, from what I've presented, I think assuming such a thing is foolish.  I don't mean to pick on Law for this.  I've seen a number of baseball people offer similar critiques.  I don't think it's entirely fair to Hendricks, though.

Kyle Hendricks isn't just elite at contact management.  He is the Katie Ledecky of weak contact.  If there were an Olympics of Inducing Weak Contact, then this is Hendricks looking back at his peers.  Jake Arrieta is lagging a bit behind.  All of his other peers fled the stadium in despair, knowing they were no match for such an intimidating foe.  This gold medal was never in question.  Another one for the red, white, and blue.  Nice job, Kyle.