Except for one that’s seemingly gone stale.
Zack Wheeler isn’t just one of baseball’s best pitchers, but one of its craftiest. He’s always experimenting, tinkering, tweaking a detail here or there. So much of pitching is about about keeping batters from getting comfortable, and Wheeler always seems to have an airhorn ready to blow next to his foes’ heads just as they’re settling down. So if I told you that he’s doing something differently to keep batters bedeviled this year, you’d probably guess it was some sort of exciting new pitch (maybe one of those trendy kick-changes all the cool kids are throwing?). Maybe a savvy change in his pitch mix, giving batters the pitches they know in sequences and numbers they’d never expect?
It’s nothing of the sort, though. He’s just getting better results from his four seam fastball and his curveball. That’s certainly welcome, but it seems remarkably mundane from an ace inventor like Wheeler. The four seamer is the most basic of offerings. The curveball is a little more dramatic, but it’s an old pitch, having been around ever since Candy Cummings got a bright idea while tossing seashells in the 19th century. These are bread and butter pitches. But as any gourmet will tell you, there’s a lot of variation in pain et beurre. The store brand stuff is no substitute for bakery-fresh. And Wheeler is proving that his Phillies cap might as well be a baker’s toque.
Here’s Wheeler’s results with the four seamer from the past five seasons.
On top of all that, his K% with the pitch has gone from 28.2% to 36.2%. Wheeler is getting better results with the heater than he ever has before. And it’s not luck: while his four seamer xBA and xSLG (.167 and .255, respectively) are slightly higher than his observed numbers, they’re still well beneath anything he’s posted before. So, how has the master craftsman changed his fastest offering? He’s throwing it at 95.8 MPH, a half-tick faster than he did last season. It’s got a tad more spin on it than it did last season (2452 RPM vs. 2431 RPM), and he’s getting ever so slightly more of that spin to work for him: 86% of his spin is “active”, meaning that it contributes to the movement of the pitch, vs. 83% last year. Correspondingly, it now has a half-inch more vertical break than it did last season. It’s not an enormously different pitch than it was in 2024, but the differences are visible.
But compare the characteristics of his 2025 heaters to those across his whole career, rather than just those he threw last season, and you see that this can’t be the whole story. The comparison to 2024 is somewhat misleading, because last season was a nadir for Wheeler’s four seamer in regards to speed, and almost a nadir for vertical break. His current 95.8 MPH speed is not the fastest he’s thrown it; he threw it as fast or faster every season from 2018 through 2023. He threw it with more vertical break in every season except for 2020 and 2024. And yet, he’s getting results unlike those at any other point in his career with the pitch now. Something changed between 2023 and 2024, and then something changed again between 2024 and 2025.
Let’s start with the change between 2023 and 2024. This one is easy to spot: he dropped his arm slot dramatically for all of his pitches. In 2023, threw his fastballs with an arm angle of 31°. In 2024, he started to throw them with an angle of 25°. That 6-inch drop is major. See, something weird happens if you throw a fastball from a low arm slot but place it high in the zone. That combination tends to baffle, befuddle, perplex, stupefy. It’s like seeing a cat standing on top of a high bookshelf. You know they can jump, but they’re not supposed to be able to get all the way up there. That additional bit of trickery can be a powerful tool in getting batters out, and so it shouldn’t be any real surprise that Wheeler, ever mutable, gave it a try. His four seam velocity and vertical break dropped alongside his arm angle, though; clearly, the new approach was a work in progress.
And he did indeed make progress with it. This season, he’s dropped his arm angle on the four seamer by an additional degree, but increased the speed and vertical movement. That can explain some of the terrific results he’s seen with it. So can this:
Here’s Wheeler’s placement with the four seamer in 2024:
And here it is for 2025:
This season, Wheeler is locating more of his four seamers in the upper corner, and fewer in the middle of the zone. In doing so, he’s showing the fuller potential of the arm slot change he introduced last season. More of those four seamers ending up high in the zone means more of those tough pitches that batters just can’t deal with. And of course, the better speed and break are helping too. The advanced stats back this up. There’s a trio of measures known as Stuff+, Location+ and Pitching+. Stuff+ measures how good a pitch is in terms of the characteristics of the pitch, but not the placement (think velocity, spin, movement, etc.). Location+ measures how good a pitch is in terms of its placement, but not its other characteristics. And Pitching+ takes both characteristics and placement into account. Wheeler’s fastball has improved in all three measures: for that one pitch his Stuff+ is up to 112 from 109, Location+ is up to 113 from 110, and his Pitching+ is up to 125 from 118. Being + stats, these are all adjusted so that 100 is average. So Wheeler’s four seamer was already well above average in terms of both its raw stuff and its placement, and now it’s even more so.
Turning to the curveball, the improvement is as dramatic, maybe even more so. In 2024, batters hit .205 and slugged .397 against it. This season? .158. For both. And if anything, he’s been unlucky with Uncle Charlie (the pitch, not Manuel): his xBA with it is 0.98, and his xSLG is .107. In 2023, he produced a whiff rate of 33% with it. In 2024, 38.7%. This year, it’s 45.5%. So, let’s ask the same question from before, but this time about the yellow hammer.
When his arm angle changed in 2024, he began to throw the curveball with less spin, and in a manner that reduced the active spin. As a result, his curveball lost nearly two inches of vertical drop, and nearly an inch and a half of horizontal break, going from above average in both to below. Strangely enough, however, his performance with it actually improved: the BA against dropped from .264 to .205, and the SLG against from .397 to .158. Only six pitchers threw a curveball with a lower arm slot than Wheeler’s 27° that season, so perhaps the confusion brought about with the odd arm angle made up for the lost movement. The tradeoff he made clearly worked. But you know what would be even better? Throwing the curve with the odd arm angle and with above-average break. Did Wheeler find a way to do that?
If you are surprised by the answer being affirmative, I have a bridge to sell you (the Ben Franklin or the Walt Whitman, take your pick). Whatever changes he’s made to his grip or motion have not just restored the spin to his curveball, but given it greater spin than it’s ever had before. He’s undone the drop in active spin % too. As a result, he’s added nearly two and a half inches of vertical drop, and nearly three and a half inches of horizontal break. He’s thrown curveballs that drop more in past years, but never one with more horizontal movement. His curve is now above average for both types of movement again. The advanced models don’t actually like the changes much: he’s dropped from 126 to 123 in Stuff+, from 88 to 79 in Location+ and from 106 to 98 in Pitching+. But the results we’re actually seeing with it are hard to argue with.
There’s one more big change among Wheeler’s arsenal, though, and this one is less pleasant. In 2024, Wheeler’s sinker was arguably his best pitch. He produced a run value of 17 with it. That was tied with Cristopher Sánchez’ change up for the most on the Phillies. Only nine pitches league-wide, and only one sinker, produced more. He posted a BA against of .188 with it, and a SLG against of .258.
This season, those figures are .354 and .688, respectively.
Granted, he’s been a little unlucky with the pitch (xBA of .278, xSLG of .498), but there’s been a real decline that luck can’t explain. He’s throwing the sinker with a little more velocity and a little more spin than last season. But it’s lost slightly more than an inch and a half of drop.
Pitch placement might be an issue, too. Though not the placement of the sinker itself.
Here’s Wheeler’s four seamer and sinker placement in 2024:
and here’s the same for 2025:
The four seamer and sinker overlapped a bit more in 2024. If a batter saw a pitch in the middle of the zone, it might be a four seamer, or it might be a sinker. But in 2025, more of those four seamers are ending up in the upper corner, where he absolutely never places a sinker. That might make it a little easier for batters to pick up on which is coming.
Like the curveball, the advanced models are a bit incongruous with what we’re observing. Wheeler’s Stuff+ dropped slightly with the sinker, but the Location+ increased, and so did the Pitching+. Perhaps that’s a sign not to be too worried: it hasn’t suddenly become a bad pitch. You can bet that Wheeler will have a plan to fix it, if he doesn’t already.
Some years ago, the pastry chef Dominique Ansel invented the cronut, creating a firestorm of enthusiasm and an a bizarre black market in which people sold the fusion sweet at a markup to those who wouldn’t brave the ever-lengthening lines outside of his shop. It was enough to establish him as a global culinary superstar. He could’ve made a career just out of cronuts. But he didn’t stop inventing: as the cronut craze faded he invented an edible shot glass made of chocolate chip cookie (and filled with milk rather than booze), frozen S’mores, so on and so forth. Zack Wheeler has taken a similar approach to his own career, endlessly adjusting, modifying, reinventing. He is the most protean of pitchers. This time next year, I’ll be writing about the changes he’s introduced for 2026. I have no idea what those will be, but I know they’ll be there to write about.