Will Warren’s One Weird Trick

Will Warren’s best pitch is a sweeper. That’s the case for a lot of pitchers in baseball today, of course, but his rendition is almost the platonic ideal of the pitch: low-80s velocity, very little vertical movement in either direction, and a huge, comic-book-exaggerated horizontal hook. The ball briefly looks possessed on its flight home:

No, your eyes aren’t deceiving you: That’s a really sweep-y sweeper. No one in baseball gets more horizontal movement on his sweeper than Warren, in fact. From his slingy, low-three-quarters arm slot, he generates the sweep the pitch is so known for, working it across the plate to righties or darting it in to steal a front-door strike against lefties. It’s Warren’s signature pitch, the secondary offering he uses most frequently, and he has it on a string. He throws it more frequently when behind in the count than ahead, believe it or not, and floods the zone with unerring precision.

The natural pairing for that sweeping slider? Warren’s excellent sinker, which dives and tails arm side, falling four more inches and tailing two more inches than your average 93-mph sinker. That movement confuses opposing hitters to no end. He’s induced called strikes on around a third of the two-strike sinkers he’s thrown all year, the best mark in the majors. You can see why:

That, in a nutshell, is the promise of Will Warren. Major league pitchers are increasingly adopting a sinker/sweeper approach when they face same-handed opposition, and Warren is one of the best there is at sinking and sweeping. That was the promise that made him a Top 100 prospect – two elite pitches, the ability to mix in a four-seamer, changeup, and curveball to keep batters off of those two premium offerings, and enough command to sew it all together. It’s working. Though he’s suffered from poor sequencing luck (65.2% left-on-base rate, one of the lowest in the majors among starters), his 2.88 FIP, 3.37 SIERA, and 3.58 xERA all point to his effectiveness so far.

Surely, then, Warren’s two signature pitches have done the heavy lifting. Let’s just take a look at our Pitch Values really quickly – they’re denominated in runs, where a positive number means the pitch has saved runs relative to average:

Wait, what? The sinker is just fine. The sweeper is terrible? His best pitch is a four-seamer?!? Who is this guy, and what has he done with the Will Warren from the scouting reports?

Here’s the crazy thing: The scouting reports weren’t wrong. Take a look at our two pitch-grading models, and you’ll see the same conclusions that our prospect team reached. Both PitchingBot and Stuff+ think Warren’s four-seamer is the third-best pitch in the sinker/sweeper/four-seamer trio. It’s not interestingly shaped or sneaky fast. Compared to four-seamers with similar velocity, Warren’s version of the pitch has average induced vertical break and average arm-side movement.

That’s a true description of the pitch, but it’s also an incomplete one. Consider that Warren’s four-seamer garners swinging strikes at the same rate as his sweeper. When he locates it in the zone and batters swing – the worst-case scenario for fastballs – opponents still miss 26% of the time. Out of 104 starters who have seen 100 swings on their in-zone four-seamers, Warren’s whiff rate is the eighth highest. Garrett Crochet, Zack Wheeler, and Tarik Skubal rank in the top five. This isn’t the kind of statistic you fake; Warren’s fastball really is wrecking people.

Even if I show you a video of it, it won’t make sense:

That’s Gunnar Henderson, of all people, looking like a clown on a 94-mph fastball right down main street. Even in a down year for him, he’s a dead-red fastball hitter. But Warren’s fastball went full John Cena – “you can’t see me.” You don’t often see someone like Henderson get de-batted by a fastball, let alone one that slow.

But why? Warren’s fastball has unremarkable movement and velocity. He’s hardly dotting the corner every time he throws it. Why does it play up so much? We could always attribute it to “deception,” that enduring catch-all, but watch his delivery up above. Does it look deceptive to you? Not really. Is it just random variation, then, some weird artifact of how many pitchers throw four-seamers? Someone has to get lucky, all of that? Seems like a weak answer to me.

If you look a little closer at Warren’s delivery, though, things start to make a little more sense. Sure, the four-seamer shape is nothing special, but he releases it from a weird place. More specifically, it’s a sinker arm slot. That’s why he’s able to get so much break on his sweeper, and so much horizontal separation on his sinker. This season, 339 pitchers have thrown 100 or more four-seamers in the majors; 304 of them throw from a more vertical arm angle. In other words, Warren’s four-seamer is weird not because it moves normally, but because it shouldn’t move normally, not from where he releases it.

For a comparison, consider the preeminent sinkerballer in baseball right now, Logan Webb. Webb, too, shows a sinker/sweeper look to righties and slings from a low arm slot. Webb, too, throws a four-seamer. He sits 92-93 just like Warren. But Webb induces 11.1 inches of vertical break on his four-seamer – low arm slot, low vertical break. Warren? His fastball rises 15.7 inches relative to spin-less flight. The average four-seamer thrown from a low, Warren-esque slot doesn’t move like this.

Here’s another way of thinking about it: Every four-seamer has vertical and horizontal movement, and that movement works out to some angle. A straight-up, north-south four-seamer would have a 90-degree angle; one that has eight inches of vertical break and eight inches of arm-side fade would be 45 degrees. That’s a different but related measurement than arm angle, which is the physical angle the pitcher’s arm makes at release. These two are certainly correlated. The more over-the-top your arm angle, the more vertical your four-seamer.

In fact, you can come up with an equation to relate the two. Warren’s fastball should feature induced movement at a 53-degree angle, just a bit above 45 degrees. Pitchers with low slots just don’t get that much rise on the ball; their four-seamers tend to be sinker-y, and they tend to be sinker-dominant pitchers. But Warren’s actual four-seamer has movement at a 60-degree angle, with two more inches of vertical break than it should have based on his delivery. It’s a lot closer to vertical than you’d expect.

This might not be your standard description of deception, but it’s clearly effective. Warren’s delivery doesn’t hide the ball from batters; it misleads them about where it’s going. Face him, and your brain will say “sinker arm slot, sinker coming.” Then the ball moves like a generic four-seamer and you pinwheel yourself into the ground swinging under it. He should throw a flat, tailing four-seamer. That’s what four-seamers from his release point do. Webb, Dustin May, and Paul Skenes throw four-seamers from similar arm slots, and none come close to the kind of shape that Warren creates.

There’s something else at play. As I’ve already shown you, Warren’s slider isn’t producing elite results at the major league level. That doesn’t mean it isn’t a fearsome pitch, though. Don’t take our pitch models’ word for it, either. It’s the breaking ball with the most break! That’s pretty clearly a good thing. Every time that Warren steps on the mound, he’s facing opponents who have read a whole packet of data about his sweeper, its best-in-class shape and movement. They’re all thinking, Don’t end up on Pitching Ninja. Don’t swing at that stupid thing. Please don’t swing at that stupid thing.

In fastball counts, that kind of pitch-expectation deception doesn’t matter much. No one’s defending against a sweeper on 2-0; hitters can sit on the Warren pitch they feel best about and try to mash it. The obvious answer for which one to sit on is his four-seamer. His sinker is hard to drive, his sweeper moves like it’s possessed by a poltergeist, and he doesn’t throw his changeup or curveball enough to be worth sitting on. But Warren accounts for that: He doesn’t throw many four-seamers in hitters’ counts.

Down 1-0? He throws four-seamers 33% of the time, below his overall 39% rate. Down 2-0? He throws them a minuscule 27.5% of the time, relying on in-zone sweepers and sinkers instead. Even in 2-1 counts, he’s only at 31%. Remarkably, his four-seam usage is higher in all two-strike counts than in any of those situations.

That leaves opposing hitters in a familiar bind. Warren’s four-seamer is a weird pitch to begin with, and he throws it most when batters are at their greatest disadvantage. If you’re trying to avoid swinging at a big looping sweeper, you might try to react and hit the fastball he throws, only to find that it moves nothing like you’d expect from his arm slot. Maybe you saw a few sinkers earlier in the at-bat, furthering the illusion. Now he throws you his weirdo four-seamer, and your eyes just lie to you.

If this sounds like an unstable equilibrium to you, I sympathize. It doesn’t make sense. His boring-looking fastball gets elite results. His beautiful breaking ball is barely missing bats. He has great peripherals and a lousy ERA. But this is a case where you should trust the granular results. His elevated ERA doesn’t come from a complete inability to manage contact. He’s not giving up scorched line drives left and right. He gets plenty of grounders and surrenders barrels at a league-average rate. He strikes out a ton of guys while doing so, and has a manageable 9.5% walk rate.

Maybe the real illusion here isn’t any one pitch but the total package. Pitchers can’t get away with a boring fastball on its own. They can’t get away with a sinker/sweeper approach all the time. Even if those pitches are great, batters are just too good these days, and it doesn’t work without the platoon advantage anyway. But mix the two, and create that fastball movement from an unconventional slot? Now we’re cooking with gas. Warren’s fastball might not jump off the page – but so long as he keeps mixing everything as well as he is now, I think the pitch is going to keep baffling hitters, and that the ERA will follow.