Staying Ahead of the Adjustment Curve, with Shota Imanaga

[Matthew Trueblood]

The Chicago Cubs' rookie ace takes the mound for the team's series opener Monday night in Atlanta. He's still the league's ERA leader, but to remain dominant, he has to keep making changes. How?

Image courtesy of © Kamil Krzaczynski-USA TODAY Sports

Everyone you know wants to talk about Shota Imanaga. Every baseball writer you've ever heard of (and maybe one or two you haven't) has jumped in to try to explain and celebrate the greatness of Imanaga's first six weeks in MLB. I can't even judge them for it, because I have been doing the same thing for months--since before he even debuted, and then right after he did so, too.

The last week or so has seen a scramble to get to the bottom of Imanaga's greatness. An MLB.com piece by the excellent David Adler dug into the characteristics that allow Imanaga's fastball to play up, relative to his velocity. (That was a theme of the above-linked piece from right here at North Side Baseball, in January, too.) Adler's piece also touched upon the uniqueness of Imanaga's splitter, which I wrote about for Baseball Prospectus in early April, and that pitch was the central focus of Meghan Montemurro's deep dive at the Chicago Tribune late last week, as well. 

Taking a bit more of a holistic tack, the insightful Kyle Kishimoto covered Imanaga's sterling work so far for FanGraphs, within which he cited the extremely detailed, novel take of Michael Rosen (at the Pitch Plots Substack) earlier in the week. Utilizing release angles on a pitch-by-pitch basis and breaking down Imanaga's mechanics in exquisite detail, Rosen discussed Imanaga's seemingly exceptional command and the way he manages to attack the top of the zone so consistently despite a low release point and arm slot.

Somehow, after all of that, I still think there are a couple of interesting things we can say, by way of updating our understanding of Imanaga as he takes the mound for the eighth time. Let's say them, shall we?

First of all, as beguiling and unique as both Imanaga's fastball and his splitter are, they will quickly see a decline in their efficacy if hitters start to feel confident of which one they're about to get. In his first couple of starts, Imanaga was very fastball-heavy, either still looking for the feel on his signature splitter or trying to establish command and consistency with the new, top-of-zone focus the Cubs have instilled in him on the fastball. Since then, though, he's steadily increased his splitter usage, making himself much less predictable for opposing hitters.

That very unpredictability has helped his stuff play up, even as the league has gotten more data on him and should be figuring him out. His splitter has earned more whiffs with increased usage, in defiance of the principle of diminishing returns. 

Very soon, I think, there will need to be more than two pitches in this mixture, to make the recipe keep tasting as good as it has thus far. Technically, of course, there already are. Imanaga has tinkered with a sinker, and he's fairly comfortable with both a sweeper and a curveball--though neither has been especially effective so far. Eventually, Imanaga probably needs one of those pitches (the sweeper is, perhaps, the best candidate) to take a step forward, but for now, he's getting by because hitters have less hope of guessing right on pitch type with each passing appearance.

The locations of those two pitches complement each other so perfectly, too, that's it's viciously hard for hitters to accurately distinguish them. Given the release angles and mechanics discussed so completely in Rosen's piece, the directions in which Imanaga's fastball and splitter diverge from one another inscrutably. From a wide angle on the first-base side of the rubber, he steers the ball across the plate with remarkable consistency, attacking the upper, glove-side quadrant.

I've said this often before, but it's funny how much it messes with hitters when a pitcher is comfortable pounding that section of the zone. It's a huge part of what makes Jacob deGrom so good, when he's healthy. Obviously, deGrom's velocity is also a key characteristic, and one Imanaga lacks, but as we've discussed before, Imanaga has plenty of other elite traits on his heater: spin, vertical movement, and a flat approach angle. 

deGrom has an exceptional slider, which breaks along the vertical line that fastball traces and bites a bit to the glove side. Obviously, Imanaga's splitter goes the opposite way, laterally, but the gist is the same.

The consistency of Imanaga's locations on those two pitches is cruel. For righty batters, especially, it looks like the fastball is coming in at the letters, over the middle or slightly inside on them, but just as often, it's the splitter, diving to about shin-high on the outer third of the plate. Soon, opposing managers will try to counter that by running more lefty batters at him, but that could make his sweeper a more effective weapon.

Let's take one last look at the splitter, though, through the lens of the new bat-tracking data released to the public via Baseball Savant on Sunday. As soon as that data hit the site, nerds everywhere (including at least four of the authors mentioned above, if you count me) were all over it, looking for interesting nuggets. Here's one I unearthed.

The new metrics don't just include swing speed. The site now also lists swing length for each hack a hitter takes, measuring the distance traveled in three-dimensional space by the tip of the bat from the beginning of the swing through the (real or theoretical, depending on whether the swing resulted in contact or not) point of contact.

As you would guess, longer swings tend to be faster swings, but they're also more prone to whiffs. Quickly, though, I realized that that's not true in equal measure for all pitch types. On fastballs, the average length of a swing that makes contact scarcely varies from that of swings that result in whiffs. On breaking balls and offspeed pitches, though, swing length matters a lot. Largely because it becomes a proxy for messing with a hitter's timing, manipulating swing length is a good way for a hurler to reliably induce whiffs on non-fastballs.

Pitch Type Group	In Play Swing Length	Whiff Swing Length
Hard	7.1	7.1
Breaking	7.5	8.1
Offspeed	7.6	8.3

This is the definition of getting a hitter out in front of a pitch that (with a velocity difference from the fastball that is a key variable in getting whiffs) is designed to do precisely that. A hitter goes to make contact in a given spot, but they're fooled, and their bat is a half-foot farther in front of home plate (and probably in the wrong place in another dimension or two) than they anticipated. Imanaga, unsurprisingly, has been very good at inducing unwantedly long swings on his splitters.

I've highlighted a few other Cubs here as points of interest and reference, but the long and short of it is simple: Imanaga gets whiffs on the splitter because he's better at getting hitters' bats out of position with it than most pitchers are on their offspeed offerings.

No team Imanaga has faced yet has posed the kind of threat to him that the Atlanta club can. Monday night could be his first tough outing of the year. The more we see (and read, and think) of him, though, the less plausible it seems that anything short of an injury can truly sidetrack the Cubs' imported ace.

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