It took some time for Bryan Woo to discover his superpower.
Today, Woo’s outlier skill — a four-seam fastball that consistently flummoxes hitters — is on full display every time the right-hander takes the mound for the Seattle Mariners. It’s a pitch that is amplified by his impeccable command, a level of precision enabled in part by perhaps the smoothest delivery in the sport.
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“First time I saw him in a game was in Double-A, and nobody could figure out the fastball,” teammate Bryce Miller said. “And they still can’t.”
Miller is correct: Opponents are hitting just .152 against the pitch in 2025, the lowest mark for any starting pitcher’s four-seamer in MLB. Its 28.6% whiff rate ranks behind only the heaters of Garrett Crochet, Zack Wheeler and Hunter Brown among qualified starters.
On a staff loaded with accomplished arms, Woo has emerged this season as the Mariners’ most dependable starter as they try to claim the franchise’s first division title since 2001. His streak to begin this season of 25 starts with at least six innings pitched and two or fewer walks was an MLB record, surpassing a mark set by Hall of Famer Juan Marichal in 1968.
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Now fully actualized, Woo’s special fastball has done wonders for the 25-year-old in just his third major-league season. But the development of this singular heater was a relatively slow burn.
‘I had one-and-a-half pitches in college’
A pitcher and infielder at Alameda High School just outside of Oakland, Woo matriculated a few hours south to Cal Poly with hopes of continuing to play both ways in college. But the Mustangs’ coaching staff had other ideas.
“I didn’t want to pitch only,” Woo recalled. “I wanted to be an infielder or two-way player. I tried to ask, like, ‘Hey, can I take some reps in the fall?’ and they kind of gave me the ‘Yeah, we’ll figure something out.’ You get to school, and of course, you don’t get anything.”
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Upon accepting his fate as a full-time pitcher, Woo bounced between the bullpen and rotation with Cal Poly. A couple of summers in the Alaska Baseball League drew a modicum of scouting interest. He began to stand out somewhat relative to his peers, but the results were poor.
“I wasn’t very good,” he said. “I had one-and-a-half pitches in college: four-seam, no two-seam. My slider was not great.”
Indeed, Woo’s ERA was 6.49 in 69⅓ innings across three seasons at Cal Poly.
“Everything was very old-school — pitch down in the zone, to the corners … and get ground balls,” he remembered. “And so I thought that my stuff just wasn’t that good, and I just had to really spot up to get outs.”
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The shoddy run prevention provided Woo minimal confidence about his pro prospects. And with an elbow injury cutting short his junior season and necessitating Tommy John surgery, the chances of his being selected early in the 2021 draft felt slim.
The Mariners, however, were intrigued. They saw Woo as a potential hidden gem. Bloated ERA be damned, Seattle wasn’t just willing to invest in Woo at the early stages of his rehab; the Mariners were ecstatic to do so. Trent Blank, the team’s director of pitching strategy and a key part of the pitching infrastructure, was insistent Seattle select Woo, going as far as to say he would draft the unproven mid-major pitcher who just had elbow surgery first overall.
What now looks to be spectacularly prescient seemed absurd at the time. But Blank saw a pitcher whose uncommon athleticism and silky-smooth movement on the mound could portend massive improvement once he was fully healthy and under the tutelage of Seattle’s renowned pitching development apparatus. And so, when Woo was still on the board in the sixth round, Seattle pounced at pick No. 174, giving him a $318,200 bonus to sign.
‘It doesn’t look like he’s even trying to throw hard’
Even before he was healthy enough to pitch again, Woo started to learn why the Mariners were so enthralled by his potential.
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“They have a presentation for you about your stuff and how it plays and what they wanted me to work on,” he recalled. “They’re like, actually, your fastball plays like this, your slider does this … and I didn’t know, like, metrics and analytics and stuff. I had to kind of learn that stuff after getting drafted, too. All of it was a little bit of a learning curve.”
Once finally back on the mound, Woo began to realize that his approach to pitching in college had been completely obscuring his greatest strength. With an unusually low release height and the unique mobility to move down the mound with ease, Woo’s four-seam fastball was a nightmare for hitters specifically when thrown at or near the top of the zone, but he’d been aiming for lower targets in search of grounders.
It helped, too, that the rehab process prioritized throwing fastballs as he built back up before reintroducing secondary offerings into the mix. As a result, Woo was able to remaster his four-seamer fairly quickly, especially with the new knowledge of how and where best to deploy it.
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“That was the one I learned the fastest how it was going to play. I was still trying to figure out slider shapes and the changeup and how I wanted those to look and to work,” he said. “But the fastball was the one that kind of came to fruition clearly the quickest, of like, ‘OK, I know that this is going to play at the top of the zone.’”
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As Woo quickly climbed the ranks, teammates and coaches in the organization were exposed to his aesthetically pleasing mechanics and notably impactful fastball. Woo and Bryce Miller, who was selected by Seattle two rounds earlier in 2021, became fast friends. But because of Woo’s rehab timeline, the two weren’t teammates until they opened the 2023 season with Double-A Arkansas.
“I didn’t realize he threw like he did until he got to Arkansas,” Miller said. “That’s the first time I’ve seen a guy that has that low of release height, with the [vertical movement] on the fastball. It’s really smooth. And you watch him from the side, it doesn’t look like he’s even trying to throw hard. [But] it’s still 95-98 [mph].”
Arkansas is also where Woo introduced a new co-star to his arsenal: a fastball of the two-seam variety, also known as a sinker. He had proven his ability to rack up whiffs with his four-seamer and improved slider, but as the quality of the opponent improved, he was in search of another weapon to induce weak contact and enable quicker, more efficient innings. The sinker did just that — and gave Woo the necessary boost to earn his first major-league call-up after just nine Double-A starts, skipping Triple-A entirely.
Blank’s optimistic outlook turned out to be spot-on. Less than one year after his first professional outing in the Arizona Complex League, Woo was in the big leagues, debuting on June 3, 2023.
‘It was heater or bust’
Pitching coach Pete Woodworth likes to stand in the batter’s box during bullpen sessions to get an up-close perspective on how his pupil’s pitches are performing. The first time he stepped in to get a better look at Woo was eye-opening.
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“Standing in on Woo’s four and then two … the difference in those two pitches, how much they moved and how well he can tunnel them — I had never really seen that before,” Woodworth said. “Luis [Castillo] is similar, but Woo’s just this really easy, smooth delivery, and then just an absolute cannonball shot — and one went this way, and one went that way.”
While throwing both variations of fastball is currently en vogue across the league, Woo takes it to an extreme. Four-seamers (47.5%) and sinkers (25.5%) account for 73% of his total pitches thrown in 2025, by far the highest rate of such offerings in tandem of any MLB starting pitcher.
The fastballs will likely always be Woo’s core competency, but his recent progress with the rest of his arsenal has fueled his breakout this season. With him having just about mastered his fastball usage in games, the days between his starts are focused on everything else.
“He just threw a pen, and it was probably 75% secondaries,” Woodworth said. “He practices those pitches and builds the confidence in those in between starts. In the game … you lean on the heaters, but he’s shown the ability to go to his secondaries in big situations and make big pitches, which he hasn’t really been able to do in years past. It was heater or bust.”
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Added Woo: “[It’s about] knowing my strengths and pitching to my strengths always, but raising the floor of the secondary pitches and consistency with those so that I can use them when I want and use them in the areas and the spots that I want … so that it allows me to come back to what I do well with the fastballs.”
Rotation-mate Logan Gilbert has watched as Woo’s gains made in practice settings manifest in games.
“The breaking balls have gotten better,” he said. “He’s working on the changeup, too. It’s always been pretty good, but I feel like he’s making some progress there this year. The fastball has always been elite … and he’s using both of them really well this year. And I feel like he knows situations that are good for two-seams, four-seams, how to mix them together, keep hitters off-track, on that kind of stuff.
“I’ve noticed him purposely finding times to take those shots, which I think is really useful, especially heading into the playoffs, heading into teams that can game-plan really well or eventually get to the heater, even if it’s really, really good. I think that really helps second, third time through, [when] you need to make a pitch at the end of the game and not having thrown five sliders all game and then you need to put one under the zone. He’s finding those times to take those shots when he hasn’t had to — because he could always go to the heater.”
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‘It’s created a lot of angry hitters’
To Gilbert’s point, as Woo continues to round out his repertoire, the four-seamer remains the moneymaker.
“It looks like he’s just throwing BP out there, and it comes out 96-97 [mph],” shortstop JP Crawford said. “I’m sure everyone who faces him is like, ‘Dude, how am I missing this?’ It just makes everyone frustrated.”
“He has some good deception in the sense of, you know, he’s so smooth, and it comes out so easy that you don’t think it would get on you like that, and it does,” said catcher Cal Raleigh, who has been behind the plate for 51 of Woo’s 69 major-league starts. “You can just tell by swings — guys feel like they’re seeing it, and they’re not. It’s created a lot of angry hitters.”
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Woo’s combination of a lower release height and a fastball that carries as much as his does gives the illusion to hitters that the ball is rising as it approaches home plate.
“It looked like it was here, but it was, like, up here every single time,” an astonished Mookie Betts said on his podcast last season after facing Woo for the first time. “I knew he was good, but seeing it … whew, golly.”
Said Gilbert: “Even if they’re seemingly on time, they’re swinging in the wrong spot, just because it stays up so long.”
Given such unusual characteristics, Woo’s four-seamer was a difference-maker even before its velocity was above-average. But the added tick this season has taken the pitch to a new level.
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“The difference between draft day and today is it’s much harder,” Mariners president of baseball operations Jerry Dipoto said. “When he first joined the organization, it would settle around 93-94 and have the same impact, but now he’s doing it at [95-97], and it just makes it that much harder to catch up with. He’s always had precision with his fastball. He can hit any one of the four quadrants from a low angle, and when you can dot up-away, up-in from that lower slot, it’s almost an impossible pitch to track.”
Empowered by the knowledge that his stuff is plenty good enough to get pro hitters out, Woo has embraced the Mariners’ mantra of dominating the zone, as epitomized by his record-setting streak of lengthy outings with so few free passes.
“The efficiency in the strike zone that’s required to do that … from start one to 25, he never got off the throttle,” Dipoto remarked of Woo’s streak. “And even in the inning where it would get away from him … an inning where it gets away from Woo is like a 22-pitch inning. He only has it every now and then. And when he has that 22-pitch inning, you know, there’s a two-inning stretch coming that’s going to be about 22 pitches and gets him back on track.”
Indeed, Woo’s 4% walk rate since the beginning of last season is tied with teammate George Kirby for the lowest mark among pitchers with at least 300 innings thrown over that span. And Woo’s 57.9% zone rate is the highest among qualified starting pitchers in 2025.
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“I think it also says something about his self-confidence,” Dipoto said. “He’s so brave in the strike zone. He’ll just attack. We preach this as a philosophy to incoming pitchers for all the time he’s been a Mariner. Same with Logan, same with George, same with Bryce. And [Woo] is the one who just said, ‘I’m in.’”
Woodworth echoed that sentiment.
“Confidence,” he said of the key to Woo leveling up in 2025. “Just knowing that you not only belong but you can be a monster in this game.”