What Happened to Garrett Crochet’s Fastball, and Why Doesn’t It Matter?

When you think of Garrett Crochet, you probably think of a lanky lefty flinging filthy fastballs past flummoxed hitters. Nearly half the pitches Crochet threw last year were four-seamers. The pitch averaged 97.1 mph, and according to Statcast’s run values, it was worth 21 runs, making it the fifth-most valuable pitch in the game, trailing estimable offerings like Emmanuel Clase’s cutter and the sliders of Dylan Cease and Chris Sale. Crochet’s other pitches were worth a combined -2 runs. Although he ran a 3.58 ERA while pitching in front of a porous White Sox defense, the four-seamer led him to a 2.38 xFIP and 2.75 DRA. Both marks were the best among all starters. Crochet has kept right on rolling in 2025. He’s running a 2.23 ERA with a 2.40 FIP, and his 4.3 WAR ranks second among all pitchers. It would be easy to glance at the top line numbers and assume that Crochet is the same pitcher he was last year, just in front of a better defense. But there have been some subtle changes under the hood, and his relationship with his fastball now looks very different.

When a trade brought Crochet to Boston in December, the reasonable assumption was that he’d back off the four-seamer at least a little. Under Craig Breslow and Andrew Bailey, the Red Sox became the most fastball-averse team in the history of the game, throwing four-seamers and sinkers just 36.8% of the time in 2024. No one expected Crochet to ditch one of the game’s greatest weapons, but it stood to reason that the Red Sox might tweak his usage just a little bit in favor of his sweeper, his cutter, and his new sinker, all of which looked like excellent pitches.

To some extent, that’s what happened. Crochet dropped his four-seamer usage from 49% to 41%, and he has arguably been even better this season. His walk and strikeout rates have moved in the wrong directions, but they’re still great, and he’s inducing softer contact with a higher groundball rate. He’s moved away from strikeouts and toward contact suppression, which is a riskier path, but it’s certainly working so far. So that’s it. Everything’s hunky-dory. But just for fun, let’s check back in on those Statcast run values I mentioned earlier:

That’s an enormous change! In 2024, Crochet’s four-seamer was his meal ticket. The slider and the cutter were nasty, but the four-seamer was the main event. This season, the four-seamer has been a net negative. It ranked fifth among all pitches last year, period. This year, it ranks 2,235th! Its chase rate has fallen from 31% to 20%. As a result, it turns into a strike 30% of the time, down from 34% of the time last season. When it gets put into play, its hard-hit rate has risen from 43% to 50%. It’s not a bad pitch and Crochet still throws it more than any other, but it’s clearly fooling batters a bit less. It’s no longer a career-maker.

I’m not positive why Crochet’s four-seamer has fallen on such hard times this season. It’s lost a tick of velocity, but he still throws it plenty hard, and stuff models like it just about as well as they did last year. Obviously, losing velocity isn’t great, but the pitch has actually added some induced vertical break. He was also throwing from a significantly lower arm slot earlier in the season, dropping from 38 degrees last season to around 31 through May. But then in June, his arm angle went right back back up to 36 degrees. Usually, more rise out of a lower slot gives you a flatter four-seamer, which is a good thing, but maybe there’s something else going on between those two variables and the way they interact with Crochet’s delivery. Maybe the arm angle hasn’t had all that much effect either way. Maybe some luck is balancing out here too, but it also looks like Crochet is throwing the pitch with less confidence:

His misses have been bigger, but he’s also being a little more fine, going for the very top of the zone rather than trusting that he can blow the pitch by batters. So if Crochet isn’t getting all that value from his four-seamer, where’s he getting it? Everywhere else:

Crochet’s overall fastball usage has only dropped a tiny bit, going from 56% in 2024 to 54% in 2025, because he has backfilled with the sinker. He only started throwing the sinker in August of last year, but by September, he was throwing it 15% of the time, and he’s roughly stuck to that usage pattern this season. Crochet leads with the sinker against left-handed batters, throwing it 34% of the time. You can see why it would be so effective. His long limbs and crossfire delivery mean that it starts behind the batter, heads away from them, then comes right back in to blast the inside corner with 16.5 inches of arm-side run.

Crochet’s sweeper and cutter have also looked unhittable, losing velocity but adding induced vertical break, like all of his pitches. The sweeper isn’t inducing as many whiffs as it did last season, but it’s dropping more and its hard-hit rate has fallen from 37% to 22%. The cutter has seen a similar change, adding some rise and losing whiffs while its hard-hit rate fell from 43% to 36%. The only pitch earning more whiffs than it did last year is Crochet’s changeup, which he only throws 5% of the time. Put it all together, though, and all of these pitches are now performing like world-beaters.

Like I said before, I can’t really explain all of this. These are real changes – velocity, vertical break, that temporary drop in arm angle – but they’re small, and at least to me, they don’t necessarily make Crochet look like a totally different pitcher. Maybe someone smarter than I am could explain all this, and I’d love to know how much, if any, of it is intentional. Lowering arm angles is all the rage these days, but it can also happen by accident. Maybe the Red Sox had a plan to optimize Crochet’s other pitches at the expense of his four-seamer, or maybe this is just how things happened to go. Crochet hasn’t made many drastic changes to his pitch mix. He’s pitching pretty much the exact same way he did last September, and the results have been the same too. He’s just putting up those same numbers in a very different way.