Why does Davis Martin have a sinker now?

One of my biggest pet peeves is when people refer to a new pitch as a “fad” or “craze.” It makes the pitch seem like a dumb parlor trick and it obfuscates what really happened. A “fad” pitch is normally some sort of breakthrough in pitching mechanics.

This is currently the case with the kick changeup.

A quick warning – we’re about to jump into some Jock Geometry. If you’ve listened to pitchers talk about pitching in the Sportrac era, these dudes sound like they have a PhD in physics. This could be a me problem, admittedly, because I have an English Studies degree and I chose my major because I could get baked out of my mind and still finish my coursework. However, I believe I’ve wrapped my head around what makes the kick change unique.

Basically, there are two ways to put spin on a baseball: supination and pronation. Supination is when you spin your hand away from your body. This makes the ball break toward a pitcher’s glove side, like a slider or a cut fastball. Pronation is the opposite. The hand spins toward the body, making the ball break toward a pitcher’s arm side. Pronation is the more unnatural motion of the two.

Maybe you’ve heard of Carl Hubbell, the Hall of Fame screwballer from the 1930s. One of his claims to fame was striking out five consecutive hitters in the 1934 All-Star Game: Babe Ruth, Lou Gehrig, Jimmie Foxx, Al Simmons and Joe Cronin. No big deal, just a combined bWAR total of 522.5, each of them helplessly flailing at Hubbell’s screwy back when All-Stars still tried.

Hubbell’s screwball was considered the great equalizer against platoon advantages because the pitch broke arm side, away from the opposite-handed hitters. It was also considered a health hazard. Hubbell’s pitching arm was functionally crippled after retirement, and he always blamed his screwball. Despite all it had done for him, Hubbell refused to teach the screwball to any of the pitchers he worked with after he joined the Giants coaching staff.

We now have other pitches that generate neutralizing arm-side run, like the sinker and the circle changeup. All those pitches still required the pitcher to pronate their arm; if a pitcher struggled with that arm motion, they were screwed (or, I guess they were un-screwed?)

Davis Martin fell into that camp. “I’ve never been a pronator,” Martin said in an interview with FanGraphs’ David Laurila in 2024. “I’ve just never been able to pronate, and post-TJ it got even worse. I’m more of a supinator now than I was before surgery.”

I’ll refrain from getting too deep into the mechanics of the kick change, but here’s the upshot: By “spiking” your middle finger upon release, a pitcher could generate arm-side run while supinating their arm. This wasn’t just a fad. It was a huge breakthrough in pitching mechanics. Supinators like Martin could now comfortably throw a pitch with arm-side run for the first time.

Make no mistake, Martin was a pure supinator. All his other offerings were supinated pitches: a slider, cutter and curve (4-seam fastballs are neither pronated nor supinated.) His slider was his main secondary pitch in 2024. He generated 3.1´´ more horizontal break on it than the average MLB pitcher, according to Baseball Savant.

Martin wasn’t just a supinator; he was a SUPINATOR.

Can you picture Martin’s slider? It’s OK if you can’t: He hasn’t thrown it once since May 3. Despite his slider leveling up to 5.2´´ of break more than average, it has been completely abandoned. His curveball is not faring much better. Martin throws it almost exclusively to lefthanders now, and its usage rate has been cut in half from 2024.

Can you guess what has replaced it?

A damned sinker! What the hell?!?

At first, I thought Statcast was misclassifying his kick changeup. The sinkers haven’t gone away, though. Their usage rate is now up to 10%, comfortably ahead of his slider and curveball. Martin’s kick changeup is also a high velocity pitch as-is; in fact, it has more velocity than Martin’s cut fastball on average.

In that same 2024 interview, Martin said he executes the kick change by “throw[ing] the crap out of it.” I don’t believe there’s any more velocity to get out of the kick change. This leads to one conclusion: Martin, who struggled so mightily with pronation that he was one of the first guys to revolutionize the mechanics of arm-side run with a supinator’s motion, has a pronating sinker that he trusts more than his slider.

I don’t point this out to say, “what the hell are the White Sox thinking?” For one, I don’t need to manufacture reasons to say that. But also, the sinker makes sense with Martin’s new 2025 pitch mix. Besides his new sinker and his dustbinned slider, Martin has thrown his cutter 8% more often this year than he did in 2024. That cutter has gone from his fourth pitch to being tied with his kick-change as his main secondary offering.

Martin’s cutter is also unique compared to most. It’s shape isn’t horizontal but vertical; it drops 3.3´´ more than the average cutter. The Savant graph is colored to make that seem like a bad thing, but it’s not. It’s just unusual.

The kick changeup also has effective vertical drop, but it also breaks much further and has more velocity. The sinker also runs inside, but does not feature that added drop of the kick change and had an additional 3 mph.

Thus, right-handed hitters must fight off two kinds of high-velo offerings on their hands and also have to cover a fastball that has the opposite sort of break that they would not only anticipate in a vacuum, but also opposite of the type of break they’ve already seen. All three pitches work off of each other well, and Martin’s release point of consistent on all three pitches.

Brian Bannister is also a big believer in developing mechanics that fit a pitcher, rather than trying to force a bunch of square pegs into round holes. In a separate FanGraphs article, Bannister says, “The manipulation of [a] pitch is a very personalized process.” It is a good thing that Bannister wants to work with pitchers as individuals, even if the mechanics take him into unexpected territory.