Should we be worried about Aroldis Chapman’s stuff?

We’re here to answer one question. Why and how has Aroldis Chapman been so bad? PSA’s own Sam Chapman dove into the Yankees Chapman’s trouble with control in 2022. Obviously that is a big piece of the puzzle, but there is more to it on top of that. Is his control all over the place because he isn’t confident in his stuff? In other words, is his potentially depleted repertoire messing with his feel and mechanics? This is certainly possible, and luckily, we can answer this for sure by looking at his pitch by pitch data.

There are three main things to look at when diving into pitch data and attempting to understand what in the world is going on with a guy like Chapman: velocity, spin, and shape. While Chapman’s velocity has been generally trending down over the last four years or so, he is quite obviously still in great physical shape.

His 97.4 mph fastball is at a career low, but as you saw in his recent outing against the Red Sox, he still pumped out low effort 100 mph fastballs with ease. I also worry about using average pitch velocity at this point in the season for Chapman. He is coming off an injury and sometimes when he is trying to find the zone, he tones it down. This season, he has found himself doing exactly that way more often. Despite that, he still has great peak velocity. Of all three factors, I’m least worried about the velocity. If there is one thing he will never struggle with, it’s athleticism and power.

Okay, so what about spin? Chapman was seemingly hit hard by the sticky substance crackdown last year. His average spin rate on his fastball in 2019 was 2,487 rpms and this year it has averaged 2,318. A combination of slightly lower velocity and lack of substances is enough to explain this. He hasn’t had the ~300 rpm drop that the Spider Tack folks had, but this isn’t an insignificant drop. It’s given his fastball a little less ride and vertical movement, and most importantly, it’s messed with his feel and grip for the baseball.

Despite that, he is still getting a ton of extension, 7.1 feet to be exact, and his vertical approach angle (VAA) sits a -5.3 degrees which is less flat than what he was at in 2019 with -5.1, but again, is not too significant. All this said, his fastball shape, velocity, and spin have all trended slightly downwards. Those three factors combined have made his fastball elite to only very good. Not super ideal, but it’s not like we can say this is an average pitch. Hitters are still only batting .182. This pitch doesn’t seem like the issue this year.

His slider is the one getting shelled. The velocity on the pitch is nearly identical to last year, but the movement profile is also slightly changed. The pitch has gone from one percent worse than average in the vertical movement department to six percent worse than average. The slider’s horizontal movement is still elite but has also seen a drop from 128 above average to 106. The spin is almost identical as well.

What does this all mean then? His two main pitches are both slightly worse in some key areas but relative to the rest of the league, he is without question still nasty. Take that and some awful control and you have yourself a pitcher who can blow away a guy on three pitches or walk the entire world. Simply put, he is more volatile than ever and having slightly worse stuff doesn’t help his cause. I’m not worried about the stuff, and I don’t think I ever will be. However, as Sam pointed out, the control is concerning and is the key for Chapman. I am worried his inability to use sunscreen or some other modest substance will have long-term effects and that this level of volatility is permanent. With as many moving parts as he has in his delivery, that slight change in feel is enough to throw it all off.