Bryan Woo Moves Like Zack Wheeler

Podcasts hosted by athletes — I don’t know about all that. But I did enjoy a recent clip from Mookie Betts’ podcast where he was talking to Cal Raleigh, who was comparing Zack Wheeler — perhaps the best pitcher in baseball — to his batterymate Bryan Woo.

“[Wheeler] is kind of like Woo,” Raleigh said. “He glides down the mound. And it’s so effortless. Some guys just have that natural glide down the mound, easy, and [the ball] just gets on you.”

Coincidentally, in a conversation in late August, Phillies minor league pitching coach Riley McCauley made the same comparison.

“[Woo] is very Wheeler-ish,” McCauley told me.

I’d messaged McCauley because I wanted to better understand how Woo’s movement related to his remarkable performance. He throws so many fastballs — nearly three-quarters of Woo’s pitches are either four-seamers or sinkers. And those fastballs are almost always in the strike zone — he ranks first among all starters in both zone percentage and walk rate. And yet nobody can square him up.

Even accounting for the three homers he allowed against the Angels on Saturday, hitters are batting .194 and slugging .304 across his 94 innings pitched. The expected stats line up with his results — his .246 xwOBA allowed is better than any pitcher this season. (Mikey Ajeto wrote about Woo’s damage suppression skills in a great post for Baseball Prospectus yesterday.)

How can Woo throw so many fastballs in the zone and walk away unscathed? I think it’s mostly because he is a pretty tall guy throwing from a crazy low release point. Standing 6-foot-2, Woo releases the ball just five feet off the ground:

Among the 115 pitchers who have thrown 500 four-seam fastballs in the 2024 season, Woo’s release height is the sixth lowest. That super low release height means his fastball enters the strike zone at the third-flattest vertical approach angle (VAA) in baseball. Only Joe Ryan and Craig Kimbrel throw flatter fastballs.

Fastballs thrown high in the zone with a flat VAA like Woo’s or Ryan’s are as close to an unhittable pitch as exists in baseball. Add in Woo’s above-average velocity (he averages 95 mph and can ramp it up to 97) and incredible strike-throwing ability, and you’ve got the recipe for a pitcher who can relentlessly attack hitters with his four-seam fastball. Even though the shape is otherwise ordinary — the pitch’s vertical and horizontal movement are both within a handful of percentage points of the league average — Woo’s release height negates these ostensibly mediocre shape concerns.

That might lead to a natural question: If throwing hard fastballs high in the zone from down low is so effective, why doesn’t every pitcher just do it? The answer is simple: Not everybody can move like Woo.

When Woo was a “midlevel” draft prospect, Trent Blank, a pitching strategist for the Mariners, told president of baseball operations Jerry Dipoto that if he had the first pick in the 2021 Draft, he’d take Bryan Woo. (Henry Davis went first overall; Woo fell to the Mariners in the sixth round.)

Blank explained why he felt so exuberant about Woo in a July 2024 interview with the Seattle Times’ Adam Jude.

“What Bryan has that’s really interesting is, he’s a guy with strength and stability and mobility, all at the same time, with good timing (in his delivery),” Blank told Jude. “You’ve got this unicorn of a mover who’s really strong and mobile… He popped for us.”

You can draw a direct line from this unicorn movement to Woo’s ability to consistently throw strikes from a low release point with above-average velocity. Each of these qualities can be explained by the specifics of his movement.

McCauley explained to me that the various positions Woo gets into are “pretty extreme,” even compared to the typical major league pitcher. What separates Woo even further from the population is that he maintains his balance while moving his body into these extreme positions.

I asked McCauley to walk me through a few of the phases of Woo’s delivery: the leg lift, the hand break, the front foot strike, and finally ball release. First, the lift:

Woo lifts his front leg way up, bringing his knee up to the letters on his uniform. The high leg lift leads directly into and influences the next phase of the delivery — the hand break, or the moment when the pitcher separates the ball from the glove.

At hand break, McCauley says, Woo extends the front of his body forward while maintaining stability on his back foot:

“This is very, very, very Wheeler-ish,” McCauley said. “The glove and the leg are both pretty extended. The hand break is pretty long, so he’s creating a ton of rotational capacity in his delivery, which is going to allow the front foot to swing open and the upper half to stay closed.”

At the front foot strike phase, Woo is engaged in perhaps the most extreme position in the delivery. As he propels the front of his body toward the plate, he’s simultaneously moving the back half of his body in the opposite direction, creating notable hip-shoulder separation.

Woo gets “a ton” of thoracic spine counter-rotation even as he orients his front hip toward the batter, McCauley says. All major league pitchers probably do this to some degree, but Woo — and Wheeler — stand out among even this elite population.

“It’s a pretty rotational lower half where he’s swinging the front leg open, but he’s mobile enough in the upper half to — you can see his chest is pointing towards us right now,” McCauley said, referring to the video frame below:

All of that lower-half movement brings Woo to his final destination way down the mound, perfectly balanced, channeling nearly all of his potential energy into the release of the pitch.

“Once that front foot hits, he’s very good at getting linear and holding, so now he’s taking that low slot because he’s creating a very stable base for that trunk to get linear and forward with,” McCauley said:

What’s remarkable about Woo (and Wheeler, McCauley points out) is that he can move like that without falling out of sequence. There are advantages to extreme positions: They help pitchers reach peak velocity and get to the devastating low-slot release point. But a typical college or minor league pitcher with a delivery like this, McCauley explained, might run into command problems by attempting to repeat this ambitious delivery pitch after pitch.

“For some guys that get in this extreme of a position, it could probably cause a lot of inconsistency,” McCauley said.

That being said, “good” pitching mechanics are not just about achieving extreme positions, but optimally timing the sequence of these positions.

Grant Messner, then a pitcher at Caltech, wrote about going to Driveline in 2018 to sort out some velocity issues; I’d recommend reading the entire post. Driveline found that one thing holding Messner back was the timing of when his hip and shoulder, respectively, hit their maximum velocity. Messner was at virtually zero seconds — to optimize his velocity, he needed it to be more like 0.05 seconds. Five-hundredths of a second, in other words, separated inefficient mechanics from perfect mechanics. And that’s just one phase of a delivery that Messner poetically describes as an “infinite-dimensional mechanical problem.”

“Guys that create positions like this — those are the guys you’re typically seeing have higher walk rates, spray the ball, get very inconsistent ball flight,” McCauley said.

As I pointed out in my article on release angles last month, the next Bryan Woo might be identifiable from a handful of pitches in front of KinaTrax cameras. The precise variables captured by a company like KinaTrax — hip-shoulder separation, core stability, leg extension at hand break, etc. — can be measured and compared to other professionals to look for outlier performers.

You could probably look at Woo’s biomechanical data, for example, and find evidence for Cal Raleigh and Riley McCauley’s observations that Woo moves like Zack Wheeler.

Wheeler and Woo both succeed because they throw high-velocity fastballs from distinct slots with exceptional command. A fastball like Wheeler’s or Woo’s “just gets on you,” as Raleigh described it. And the ability to throw that fastball can be connected directly to the way these pitchers “glide down the mound,” harnessing athleticism that stands out even among the super talented people who throw baseballs for a living.

“This is subjective, but from what I’ve seen, the bigger positions you get into, it’s going to be harder to create tension and throw strikes in those positions,” McCauley said. “But that’s where you get guys — like Joe Ryan or Wheeler or Woo — who have somehow found stability in these crazy positions. You’ve now created a monster of a guy that has elite command and very unique delivery. And now you’re talking about a beast.”