Shohei Ohtani, Dean Kremer, and Fastballs That Aren’t as Fast as Other Fastballs

There are two predominant fastball types in the majors these days: the four-seamer and the sinker. The cutter usually gets categorized as a fastball too, and for some pitchers, like Corbin Burnes and Kenley Jansen, it certainly is one. Then again, most pitchers use their cutter as a secondary or tertiary offering, and the average cutter comes in at 89 mph; that’s closer to the average changeup than the average four-seamer. The cutter defies simple classification. Then there’s the split-finger fastball, which is nothing more than a misnomer. It’s an offspeed pitch, no doubt about it, and therefore “splitter” is the more widely accepted label nowadays.

So, back to those two fastballs. The four-seamer is essentially the “throw it as hard as you can” ball; if you hear someone use the generic term “fastball” to describe a particular pitch, this is the one they’re talking about. In terms of grip, a four-seamer isn’t all that different from the way any other fielder throws the baseball. The sinker, on the other hand, is a more specialized weapon. As the name suggests, it has more movement than a four-seam fastball, and it’s more useful for inducing weak contact than blowing the ball past the opposing batter. Yet, modern pitchers have been taking that “throw it as hard as you can” approach with their sinkers as well. Over the past four seasons, the average sinker is only 0.6 mph slower than the average four-seamer.

Thus far in 2023, 52 starting pitchers have crossed the 50-inning threshold while using both a four-seam fastball and a sinker at least 3% of the time. Of those 52, 83% throw both pitches within 1 mph of one another. All but two throw both pitches within 2 mph of one another. As you might have guessed, I’m here to write about the two exceptions, the two starting pitchers who throw their four-seamer and sinker nearly 3 mph apart: Shohei Ohtani and Dean Kremer.

Ohtani introduced his sinker last season to much fanfare. To be fair, Ohtani could introduce a new haircut to much fanfare, but his sinker really did deserve the attention. He debuted the pitch at 97 mph in mid-August, and by September he could touch triple digits. According to Pitch Info, Ohtani’s new weapon was the second-most valuable sinker (on a rate basis) among qualified American League starters.

In 2023, that sinker hasn’t been nearly as fast, nor has it been nearly as effective. Ohtani’s average sinker is clocking in at 94.2 mph, three ticks slower than last year and just about three ticks slower than his four-seam fastball. The Stuff+ on his sinker is down from 109 to 103. Opposing hitters are swinging less, whiffing less, and making better contact:

Kremer’s story is almost the mirror image of Ohtani’s. When the 27-year-old Orioles pitcher introduced a sinker of his own last August, it didn’t garner much media coverage (indeed, his hair might get more fanfare than the rest of him). It also didn’t have much success. From August to October, his sinker was the least effective pitch in his arsenal. On a rate basis, it was the least valuable pitch he threw all year. Unlike Ohtani’s blistering sinker, Kremer’s 91.6-mph version of the pitch was one of the slower sinkers in the game. Opposing hitters punished it to the tune of a .369 wOBA in August and a .455 wOBA in September.

Considering how hittable his sinker already was, it certainly wasn’t a pitch Kremer would want to throw any slower, and he isn’t. Remember, this is the mirror image of Ohtani’s story. Kremer has widened the gap between his two fastballs by throwing his four-seamer faster than ever. For the first time in his career, he throws his four-seamer harder than the average starting pitcher. It now sits around 95 mph, topping out at 97.5 mph, while his sinker is still around 92 mph.

A soft-tosser during his early days in the Orioles’ system, Kremer can now bring some legitimate heat. But if he has that heat in his arm, I’m curious why his sinker hasn’t experienced a similar uptick in velocity. Similarly, I wonder why Ohtani is throwing his sinker so much slower this year when we know he has it in him to throw one of the fastest sinkers in the game. Several factors go into crafting the perfect pitch, but as a general rule, fastballs are better when they’re fast. Because sinkers have more movement than four-seamers, they aren’t quite so reliant on velocity, but the principle still holds true. All else being equal, hitters perform worse against faster sinkers:

What Ohtani and Kremer are doing isn’t entirely unheard of, but it is unusual. Last year, Ross Stripling led starting pitchers (min. 120 IP) with a four-seamer/sinker velocity gap around 2 mph; Kremer was right behind him. In 2021 and 2019, the biggest velocity differential belonged to J.A. Happ. In addition, Rich Hill has maintained a wide gap between his four-seamer and sinker over the past several years, although he only uses his sinker 2-3% of the time.

However, what sets Ohtani and Kremer apart from all those other pitchers (including Kremer’s past self) is that they’re capable of throwing high-velocity pitches. Stripling and Happ were averaging 91-92 mph with their four-seam fastballs, and Hill can only hit 90 on a good day. Pitchers like that need some tricks up their sleeves to succeed. But Ohtani and Kremer (and especially Ohtani) don’t need to rely so heavily on mixing speeds, and even if they did, they both have six-pitch arsenals to work with. So why are these two starters choosing to forgo velocity on a pitch that is supposedly a fastball?

Unfortunately, I don’t have an easy answer to this one. In Kremer’s case, I wonder if his sinker velocity will rise with time. After all, it’s still a relatively new pitch for him, and his increased four-seam velocity is newer still. He might just need some more practice with the sinker before he’s ready to turn up the heat. Then again, his sinker has been his best weapon this year, according to Pitch Info and Baseball Savant, and it’s been his most improved offering per PitchingBot and Stuff+. He might not need that velocity bump after all.

Kremer’s sinker is working particularly well in conjunction with his four-seam fastball. He’s been throwing more sinkers in the zone this year, which he can do because he’s keeping hitters off guard with velocity differential and not just movement. This, in turn, gives him more freedom to throw his four-seamer up and out of the zone, an area where his four-seamer thrives. He has also added some horizontal break to his four-seamer; that gives it a more similar movement profile to his sinker, but that’s not such a problem when the two pitches are different speeds.

In addition, Kremer is throwing his sinker with significantly less spin this year. Last season, his sinker was spinning at 2,139 rpm, perfectly normal for its speed. This year, Kremer has reduced his spin rate to 2,028 rpm even though his velocity is actually a few tenths of a mile faster. Accounting for velocity, he now throws one of the least spinny sinkers in the game. Low-spin fastballs tend to induce more groundballs, which is usually the desired effect of throwing a sinker. Thus, perhaps Kremer is more concerned with keeping his sinker spin rate as low as possible than increasing his velocity. If that’s the case, he’s doing a splendid job so far.

As for Ohtani, I have even less of an answer, although I’m certainly willing to give him the benefit of the doubt. Stuff+ and PitchingBot agree that his sinker has worse stuff this year, and opposing batters are having much more success against the slower pitch. Ohtani has spoken about feeling some fatigue this year, so perhaps he’s just not throwing as many max-effort pitches. I’m not satisfied with that explanation, though. Ohtani doesn’t use his sinker often enough for it to make a huge difference, and I don’t think he would choose to throw a less effective fastball just to save a little mileage on his arm.

It’s not as if Ohtani is taking a new approach with his sinker that could justify the missing velocity. He’s using the pitch a similar amount of the time, and he still favors it early in the count. Almost 80% of his sinkers have come on the first two pitches, while only 8% have come with two strikes or three balls; that’s no different from his approach last season. What’s more, Ohtani is actually spinning his sinker more this year, even though his velocity is so much lower. Last season, his sinker was spinning at 1,973 rpm, which is shockingly low for such a fast pitch. This year it’s spinning at 2,025 rpm, still on the low end of the spectrum but not quite so unusual.

It is worth mentioning that Ohtani’s velocity differential has been smaller and his sinker more effective against right-handed batters. Like most pitchers, Ohtani primarily uses his sinker against same-handed opponents. And if you only look at the numbers against righty batters, the gap between his four-seamer and sinker is smaller. That’s because he’s thrown his four-seamer about a tick faster against lefties. Meanwhile, the handful of sinkers he has used against lefties have been strangely slow:

And I said, Ohtani’s sinker has been more successful against right-handed batters. It’s still not as impressive as it was last year, but a .288 opponents’ wOBA and .259 opponents’ xwOBA are both respectable numbers. All this to say, if you disregard his sporadic sinker usage against opposite-handed hitters, Ohtani’s sinker isn’t as much of a mystery. The velocity gap between his sinker and four-seamer is still unusual but not to as great an extent, and his sinker hasn’t been as ineffective as it looks at first glance.

In an age of ever-increasing velocity, it’s fascinating to see a couple of pitchers who are seemingly electing for less velocity on one of their fastballs. It may seem counterproductive, but that’s exactly why it’s so cool. Pitching is both an art and a science, and it wouldn’t be either without a little room for outside-the-box experimentation.