Bryan Woo Is a Low-Slot Success Story

Bryan Woo wasn’t highly regarded when the Seattle Mariners selected him in the sixth round of the 2021 draft out of Cal Poly. That’s understandable. The low-slot righty had a 6.36 ERA in his three collegiate seasons, including a 6.11 mark in his injury-hampered junior year. After undergoing Tommy John surgery in April 2021, he made his professional debut in ’22.

Now, the 24-year-old is showing that Seattle’s director of pitching strategy, Trent Blank, wasn’t completely out of his mind when he reportedly told members of the Mariners front office prior to the draft that “this guy would be one-one for me.” While it’s unlikely that Woo is going to be as good or better than all of the 173 players drafted ahead of him, his numbers have nonetheless been impressive. Since making his big league debut in July 2023, he has a 3.60 ERA and a 3.96 FIP over 137 1/3 innings across his 28 starts with the Mariners. In 10 outings this year, he is 4-1 with a 2.54 ERA and a 3.25 FIP. It’s worth noting that this success hasn’t exactly come out of nowhere. Including four rehab outings this year, Woo logged a 2.97 ERA and 162 strikeouts over 115 innings as a minor leaguer.

Woo brought up his backstory when I asked him how he’s developed as pitcher.

“Going through the draft-and-scouting process, I feel like a lot of it was based on my potential,” Woo told me when the Mariners played in Cleveland last month. “I didn’t have great results at the time. It was based off of, ‘He could be this. It looks like he’s developing into that.’ For me, it was about believing that I could get there, that I could continue to get better. That’s kind of the story. I wasn’t too well-known. If you look at in on paper, it was never, ‘This guy is really good.’ The numbers never really showed that I was.”

Not surprisingly, Woo also brought up the fact that he’d been injured when he was drafted, and how that made for a lot of uncertainty. As he put it, “I didn’t quite know what was going to happen. It could have been a little higher. I could have gone a lot lower. I really wasn’t sure.”

He did know that his repertoire needed both refinement and enhancement. The Oakland native had a mid-90s four-seam fastball when healthy but nothing else to write home about. His slider, which he described as having been “OK,” was a pitch he’d throw here and there. He also had a changeup, but that mostly sat in his back pocket.

Developing a second heater has been especially impactful for him. He added a two-seamer to his arsenal last year while toeing the rubber for the Arkansas Travelers.

“Last year, before I got called up, our pitching coordinator came down to Double-A, where I was at,” Woo said. “He sat in on one of my bullpens and said, ‘Just try it.’ I was having a lot of high pitch count games — I wasn’t getting many quick outs — and he said that it could be a tool to use to get some quicker outs, some weaker contact. A lot of my game was strikeouts and fly balls. There weren’t many efficient outs, I guess you could say. So, we tried the two and it has progressed from there.”

So far this season, Woo has thrown 51.4% four-seamers and 27.2% two-seamers, as well as 7.2% changeups, 7.1% sweepers, and 7.0% sliders. The last of that mix, according to the righty, acts more like a gyro when he throws it low, and more like a cutter when he throws it toward the top of the zone. His circle changeup is a pitch he described as having “a little less vertical and a little bit more horizontal, as well as little bit slower, than my sinker.” Asked which of his off-speed pitches he sees as his main secondary offering going forward, he said that he’s satisfied with the progress of all three and wouldn’t take one over the other.

As for his two fastballs, the 6-foot-2 Woo wasn’t inclined to pick between them either. Instead of choosing favorites, he described why he’s had success with his heaters despite their relatively unimpressive metrics.

“Neither one plays super high metrically; the vertical and horizontal movement aren’t anything crazy,” Woo said. “I think it’s just my slot, kind of how the ball comes out, that makes them a little bit different.”

The slot is indeed different. As Pitcher List’s Jack Foley explained last summer, “At 4’11” off the ground, Woo has a release height a full foot below the average.”

Woo told me that he was more over the top in high school, only to have his arm “kind of lower on its own throughout college, post-surgery, and pro ball.” He claimed to have never purposefully dropped it down, but rather has just continued to throw in a way that feels most comfortable. Not so comfortable are opposing batters. They have just a .220 xBA and a 2.7% barrel rate against the low-slot righty this season. When healthy — he missed the first month with elbow inflammation and later was on the shelf for three weeks with a hamstring strain — Woo is hard to square up.