Bryan Woo has dominated in his sophomore season for the Mariners, tossing 99 innings in 18 starts with a 2.36 ERA and 3.30 FIP. After a rookie season in 2023 with a 4.21 ERA and 4.36 FIP, Woo has entirely shored up his walks, limited home runs, and induced weak contact, all while striking out fewer hitters than before.
The 24-year-old starter was a sixth-round pick for the Mariners in 2021, and quickly climbed through the minors towards his debut just two years after he was drafted.
While his success itself has been a pleasant surprise, the means by which he’s dominated is far from what would be expected when considering his past performance.
What’s Changed?
On the surface, we’ve seen Woo sacrifice strikeouts in exchange for limiting walks, similar to his teammate George Kirby. Still, Woo going from a league-average 8.4 BB% in 2023 to a minuscule 2.4 BB%, which leads MLB among pitchers with at least 75 IP, is a drastic improvement.
While this has led Woo to see his Whiff% drop from 28.1% to 21.1%, he’s also getting more ground balls and inducing weak contact.
This is a far change from Woo’s career thus far, including the minors. While his longest MiLB season came with a 4.11 ERA in 57.0 innings, his 13.3 K/9 would suggest more strikeouts in 2024 compared to 2023 once Woo had a larger Major League sample.
In his case, Woo’s other skills, such as his elite command, suggested he could get results without generating high strikeouts, but instead limiting walks and barrels, which has paid off tremendously.
This stems from a few changes to Woo’s approach, although not entirely in the way you might expect.
In 2023, Woo’s overall stuff graded out about league average across the board – with what was average command and a solid but ordinary arsenal, it made sense why Woo was a league-average starter.
While Woo hasn’t had a full 2024 season, his 18 starts have provided a large enough sample to suggest Woo has taken massive steps forward in his game.
Surprisingly, Woo’s pitch usage didn’t change too much. While he converted his cutter/slider into a slider/sweeper and bumped up his changeup usage, he is still firing his four-seam or sinker about 70-75% of the time.
For how little damage Woo allows, his fastball usage is unique – as his league-best 2.4 BB% suggests, he throws in-zone far more frequently than most other starters. His fastball usage best displays this; while his four-seam and sinker are both in-zone a ton (57.9% and 66.8%, respectively), they do completely different things.
Woo’s four-seam grades out above average thanks to his good shape and unique approach angle, resulting in it generating extreme fly balls (27-degree average LA) and whiffs (14.3 SwStr%) while limiting hard contact (87.5 mph average fly ball EV).
Woo’s sinker is a similarly great pitch, although it took massive strides in 2024 as its average PLV climbed from 4.64 to 5.47. Somehow, no real improvements to its shape contributed to this, but his command of the pitch improved drastically.
Woo went from focusing the pitch arm-side and low, which is common for sinkers, to instead throwing in all parts of the zone. This change not only allows his sinker to induce ideal contact (69.2 GB% and 86.3 average EV) but also generate called strikes at an elite rate (27.3 CS%, up from 20.0 in 2023).
Woo uses his changeup for a similar purpose, which allows his sweeper and slider to get chases and whiffs. His sweeper, which has 12 more inches of glove-side break than his slider, is often out-of-zone while his slider is more frequently in-zone. Both pitches generate excellent results, and Woo’s command of his sinker and changeup in similar locations allows them to complement each other well.
The Outlier Talent
In a few ways, Woo has abilities that I’d say are an outlier. At only 24 years old, Woo has the talent that most veteran pitchers would wish for.
This stems from Woo’s ability to have such an impressive arsenal that he pairs with his elite command. Not only is his 2.4 BB% tops in the league, but he still manages to induce weak contact (88.3 average EV), avoid barrels (4.1 Barrel%), and of course limit runs (2.36 ERA and 2.52 xERA).
Woo’s also unique in his mechanics; his 5′ release height with 6.6′ of extension is an incredibly rare pairing, which allows his four-seam to play up when executed higher in the zone, among other things. To learn more about Woo’s unique mechanics and elite athleticism, be sure to check out Michael Rosen’s article with Fangraphs as well.
Having this as a part of his skillset, along with his incredible ability to command the rest of his arsenal, suggests Woo truly does have the talent to sustain most of his results. While his 2.36 ERA may regress closer to his 3.30 FIP, Woo has the talent to sustain his minuscule BB% and 108 Location+.
In addition, if Woo’s stuff were to regress, he’s shown the ability to work around results and implement changes when he’s had to. While you’d like to see Woo generate more whiffs in the future, his elite ability to avoid ideal contact and limit baserunners will be enough to make him a well-above-average pitcher in 2024 and beyond.