Aroldis Chapman's late-30s run can all be explained by one stat

On Thursday, I asked Dan Szymborski what he thought explained this crazy late-30s Aroldis Chapman run, and he said his hunch was that the lefty was “a lot less cute on first pitches than he used to be” — even though he couldn’t quite prove it. So I looked into just that, and while I don’t know if first-pitch strike percentage is the same thing as “not being cute,” Chapman has been throwing way more first-pitch strikes than he ever used to, up from 58 percent in 2024 to over 70 percent in 2025 and 2026. I think Szymborski might have been onto something.

So Chapman is throwing more 0-0 strikes. Great, but why? You could chalk that up to a 37-year-old in his 16th season suddenly developing top-tier command on first pitches without a drop in velocity, but I have a different theory: It’s the sinker.

The secret to Aroldis Chapman's longevity is a pitch change

Everybody loves sinkers; they’re a velocity pitch that bites, capable of creating both swing-and-miss and produce ground balls. Chapman’s sinker is special, though, in that he throws it in the high 90s and forces hitters to guess between that and a four-seamer. Along with a murderous slider and splitter, that’s not really a situation you want to be in. He appears to have realized this, too, and has ratcheted up his sinker usage in recent years even before coming to Boston. But once he got there, it looks like the pitching staff sat him down and said, “hey, you know that sinker? Yeah, throw that.” 

Chapman has shown an ability to command sinkers in a way that makes it impossible to hit. His sinkers drop hard visually for hitters because of Chapman’s super vertical arm slot, while his four-seamer actually rises a bit. Both are coming at you at around triple digits; in short, you have to guess. That sounds horrible.

Aroldis Chapman's sinker isn't like other sinkers

This coin flip from hell has allowed Chapman to pound the zone with impunity, finishing with the third-lowest in-zone contact rate among in 2025 among all pitchers. He’s a tick higher in 2026, but he’s still 11th best. He posted a career-high 3.6 WAR in 2025, and is actually on pace for even more saves in his age-38 season. It’s pretty cool stuff, and the sinker correlation is clearly our explanation. So we’re done here, right? Pack it up?

Heck no, it’s time for the real nerd stuff. Please open your hymnals to “the effect of spin direction on sinker launch angle,” because Chapman’s undergoes zero shift relative to his four-seamer — something noted as not-a-good-thing by Justin Choi in his foundational text for the Sinker Church in 2021: “A Few Interesting Facts About Sinkers”. Choi showed how spin difference was inversely correlated with launch angle, meaning that the more you can spin your sinker the more likely you are to get ground balls.

But the only difference, apparently, between Chapman’s sinker and his four-seamer is that one sinks and one does not — the spin is not substantively different, which should be a negative for Chapman. But I just said that his sinker usage is the reason for his success. So what gives? 

Using a sinker as a true strikeout pitch is what makes Aroldis Chapman's so effective

Choi mentions Miguel Castro, a former turbo-sinker enjoyer, as evidence for why spin shift from your four-seamer matters. Castro’s sinker didn’t shift at all, and it wasn’t a super effective pitch at producing ground balls or … really doing much of anything. But Castro also didn’t use his sinker to put away hitters at all. It was not a strikeout pitch. For that, he employed his slider.

But for Chapman, the sinker is unique because it is a strikeout pitch. Between his sinker and four -seamer, the former had nearly triple the latter’s K rate last year and double this year. Chapman is not a ground-ball pitcher; it just isn’t hit approach. He is looking to bombard hitters with fireballs and get them down on strikes. The sinker has allowed Chapman to continue attacking hitters like he always wants to with a pitch he seems able to command. Because it isn’t anyone else’s sinker: It’s the Aroldis Chapman sinker, and that’s why it’s been successful. Oh … also, it’s like 100 mph. That too.

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