The Huge Swing Plane Adjustment Pete Crow-Armstrong Has Already Made, and the Huge Approach Change Still Needed

[Matthew Trueblood]

The Cubs' firecracker of a center fielder came up swinging fast and free, and missing everything. Now, he's figured out how to square up the ball--but a key tweak must come next.

Image courtesy of © Daniel Kucin Jr.-USA TODAY Sports

By now, the numbers might be familiar to you. Let's rehash them, though, because this turns out to be one of those times when selective endpoints are valuable tools, rather than red herrings. Through Jul. 26, Pete Crow-Armstrong was batting .180/.230/.292. For reference, in the years 2000 and 2001, Kerry Wood batted .216/.242/.261. From 1998 through 2001, then-Expos starter Javier Vázquez batted .235/.266/.281. There's an old tweet saying that the most vicious burn you can hurl at someone is, "Who is this clown?", because it not only calls the target a clown, but implies that they're not one of the better-known clowns. For his first 200 big-league trips to the plate, Crow-Armstrong not only hit like a pitcher, but hit like a fairly unremarkable offensive pitcher.

The next day, everything changed. Rare--excruciatingly rare, almost unheard-of, and often only illusory--are cases in which everything changed for a hitter on one day, but it's hard to make any other case with Crow-Armstrong. Very visibly, that day, he went to a bigger, more rhythmic move with his lower half--a leg kick--in the load phase of his swing. Less obviously, but just as importantly, he debuted a slower but infinitely more controlled swing, with a much more on-plane bat path.

New bat-tracking data made available to the public this spring via Statcast has allowed us, for the first time, to measure the efficiency of a player's swing. It's simple, though far from easy for us laypeople: given the observed speed of the incoming pitch and the player's bat, what is the maximum possible exit velocity, had the two met perfectly squarely? And what percentage of that theoretical maximum did the hitter achieve on a given swing?

Here's a rolling chart showing the Squared Up% of Crow-Armstrong's swings, courtesy of Kyle Bland, a data whiz who works for PitcherList and ginned up a supremely useful app to digest bat-tracking data within a couple of days of the information becoming available. See if you can spot July 27.

Again: baseball data just never tells you this neat a story. Transformations that radical do not happen that quickly. One day, Crow-Armstrong was limping along, struggling to square the ball up and create any real damage against big-league pitching. The next day, he began teeing off on almost everything. Since that day, Crow-Armstrong is hitting .330/.378/.551. He's become the heart and soul of the Cubs' offense, even as their everyday No. 8 hitter. In 121 plate appearances, he's only struck out 18 times, and he has 13 extra-base hits.

Almost paradoxically, he started hitting it hard more often, hitting it harder on average, and reaching higher top-end exit velocities, all while both making more contact (which usually means accepting some weaker contact along the way) and swinging the bat slower. Wait, what? 

Yes. The above demonstrates the jump in Crow-Armstrong's contact efficiency. With this chart of his swing acceleration over time, we can see that that efficiency made up for a material sacrifice in terms of raw bat speed.

Part of this is, simply, that Crow-Armstrong's adjustment both got more balls onto his barrel (rather than being mishits) and led to more contact, in general--as opposed to whiffs. During June and July, especially, his swing was very fast, but also steep and out of his careful controi. He had to guess at pitch type and location, fire, and hope to run into the ball. Even on hittable pitches, he often failed to do so.

There's no question that adding a leg kick helped cue Crow-Armstrong to be more deliberate about seeing the ball. His swing now has phases and flow, and those things require a bit more reactivity, a bit more balance. It's why he's not missing hittable pitches much at all anymore, and why he can hit them with authority, even while lacking elite bat speed.

Here, alas, is where I jerk the chain--just a little bit--to rein us all in. You didn't think this would be simplicity and sunshine beginning to end, did you? See, when he was going truly dreadfully, Crow-Armstrong's biggest problem was a lack of plate discipline so profound it could make Javier Báez (or Javy Vázquez, for that matter) blush. Crow-Armstrong chased almost half the pitches he saw outside the zone in June and July, trying to make things happen and to avoid falling behind in counts against pitchers whose polish, sequencing, and command he could not handle.

Since making his mechanical change, he's also changed this--kind of. Here are his swing rates on pitches inside the zone, and beyond it, throughout the season.

Seeing that blue line trending steadily downward will warm the cockles of any hitting coach's heart. That's pixelated job security, right there. That's a young hitter taking great instruction and screaming around a developmental corner at full speed. Only, look at the yellow line, too. That one is telling its own story. At his peak, in the first half of August when he was first starting to really feel his new superpower, Crow-Armstrong was swinging at fully 90% of the strikes he saw.

I don't care if you're the secret grandchild of Ted Williams and Rod Carew: you can't sustain a high level of contact efficiency while swinging at over nine of every 10 pitches in the zone--let alone chasing barely a quarter of the time in the process. That bespeaks a hitter on a true, once-in-a-lifetime heater--but not one who has figured out the game in some semi-permanent way.

Crow-Armstrong, in short, still needs to learn to swing less often, and this set of adjustments to his setup and swing hasn't much helped with that. I can buy that he's going to cut his chase rate into the 30s, rather than the mid-40s, and that's plenty valuable, but until he gets more selective across the board--even within the zone--there will be pitchers getting his report and nodding purposefully. At key moments, teams will start figuring out ways to retire Crow-Armstrong, by exploiting his hyper-aggressiveness.

That does not, by any means, invalidate the huge changes he's made. They should continue to serve him well. The Cubs seem to have a credible big-league hitter on their hands, thanks to the way he's changed his usage of his. They just don't have a bona fide superstar, unless and until a very difficult--and, for many afflicted with such swing happiness, impossible--second layer of major changes is made.

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