Only now, with the perspective of time and experience, can Bryan Woo look back at what he was as a rookie two years ago and recognize the honest truth.
He had no idea.
No idea who he was as a pitcher. No idea what it took to be a successful major-league starter.
“I didn’t really know myself,” Woo said, “or what worked for me.”
Early in his career with the Mariners, Woo prioritized recovery and rest between starts. At the time, that’s what he thought his body needed to be ready to pitch every fifth day.
His mentality has flipped, and with it his place in the Mariners’ starting rotation.
Woo’s emergence as an ace is one of the most promising developments of the season for the Mariners, and it has happened at a most critical time as the M’s navigate injuries to Logan Gilbert, George Kirby and Bryce Miller, three-fifths of a rotation that ranked as the best in MLB in 2024.
The Mariners’ main five starters — Gilbert (33), Kirby (33), Miller (31), Luis Castillo (30) and Woo (22) — combined to make 149 starts last year. (Emerson Hancock made 12 and veteran lefty Jhonathan Diaz made one.) The M’s rotation led the majors in innings pitched and ERA, and the staff set the MLB record for highest average fastball velocity (95.6 mph).
They were as durable as they were dominant.
Until they weren’t.
Just a month into this season, as injuries mounted, the Mariners already had to turn to a seventh different starting pitcher, matching their total from 2024. Diaz, recalled Wednesday when Miller was placed on the injured list, would be the eighth if he makes a start on this 10-day, 10-game road trip.
“You don’t expect the injuries and stuff for our staff, as healthy and consistent as we’ve been the last couple years,” Woo said. “So, really, just trying to hold it down until those guys get back and we get back to doing what we do.”
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A year ago, no one would have reasonably suggested that the 25-year-old Woo would stand as the Mariners’ most dependable starter.
The talent was never a question. Woo’s athleticism and his uniquely low arm slot were among the main reasons Trent Blank, the club’s director of pitching strategy, told the Mariners front office that he would select Woo with the No. 1 overall pick going into the 2022 draft.
Durability was a question. Woo had three stints on the injured list in his first 12 months in the majors with forearm, elbow and hamstring issues.
From start to start, it wasn’t certain which version of Woo would show up on the mound. On July 27 last year, Woo exited a start after four innings against the White Sox because of hamstring discomfort.
That truncated outing prompted a request from catcher Cal Raleigh for a sit-down meeting with the young pitcher when the team arrived at Fenway Park in Boston.
Woo hasn’t been the same since.
“That was the turning point for him,” M’s pitching coach Pete Woodworth said this week.
After that conversation with Raleigh, Woo pitched into the seventh inning in each of his next six starts; he’d never pitched past the sixth inning in his first 29 career starts.
That consistency has carried over in 2025, and Woo ranks among the best pitchers in the majors through his first eight starts, posting a 2.84 ERA, a .089 WHIP and a 50-to-8 strikeout-to-walk ratio in 50 2/3 innings.
He’s baseball’s only pitcher to complete six innings in every start so far this season.
And since Aug. 1, 2024, Woo has thrown 118 1/3 innings, the fifth-most in MLB in that span, and his 3.3% walk rate ranks No. 1 among all starters.
“He’s much more, like, truly confident,” Woodworth said.
On Tuesday, Woo outdueled Yankees ace Max Fried by throwing 6 1/3 scoreless innings in the Mariners’ much-needed 2-1 victory, strengthening his case for his first All-Star selection this summer.
Raleigh recently dubbed Woo “The Stopper” of the M’s staff. And in an indication of just how valuable he’s become, the Mariners opted to push Woo’s start up a day to Sunday so he can face the San Diego Padres in their series finale at Petco Park. (With Thursday’s off-day, Woo will be pitching on normal rest.)
Watching his teammates develop a “workhorse” mentality the past couple years motivated Woo to try do the same.
And here he is.
“It’s something I always wanted to do and wanted to be,” Woo said, “so just trying to be that as much as I can.”
Woo still relies heavily on his four-seam and two-seam fastballs, throwing them a combined 69% of the time and ranking in the 99th percentile in fastball value, per MLB Statcast metrics.
But his secondary pitches — slider, sweeper, changeup — have taken a major leap. As a rookie in 2023, his breaking ball value ranked in the 16th percentile; this year, it’s up to the 86th percentile.
“He can execute secondary pitches at a much higher rate,” Woodworth said. “It’s not just, ‘All right, let’s hope we can beat ’em with these two fastballs.’ He can pitch, and that just adds to your confidence because you have more weapons and more ways to get guys out.”
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To be fair, it’s understandable that Woo, at age 23, didn’t know who he was or what he wanted to be when he arrived on the scene with the Mariners in June 2023.
He had made his pro debut — in rookie ball — less than a year earlier, and he’d thrown a mere 101 innings in the minor leagues before earning an MLB promotion. He’d also thrown just 69 innings in college before having Tommy John surgery in April 2021.
“Getting used to a big-league schedule was definitely no joke, especially for someone who just didn’t know a whole lot,” Woo said. “I just had very little experience the minor leagues and then getting called up. So that was just a learning process and figuring that out as I went, and then finding some stuff that worked at the end of last year.”
Rest and recovery, while still important, have become a secondary part of his between-starts routine. He’s learned he needs to push himself physically, something Raleigh urged him to do during that conversation in Boston.
“You’ve got to put in the work every day,” Woo said. “There’s no, ‘Oh, I’m going to take it easy for four days and then go pitch.’ You’ve got to get after it in the weight room. You’ve got to make sure your catch-play has intent behind it.
“I thought it was more, you want to make sure you rest and recover and making sure you’re taking care of yourself that way. But it was actually kind of the opposite.”
He’s also grown close with Adam Bernero, the team’s mental performance coach.
“‘Bern’ has been huge for me,” Woo said.
His confidence these days, he said, comes from his preparation.
“You know you’ve put the work in on every part of it — throwing, lifting, treatment, recovery, all that stuff,” he said. “You’re just doing everything right, so for me I look at that fifth day as kind of the easiest day. You don’t have to think about it. Just go out and pitch and let your stuff play.”
