clock menu more-arrow no yes mobile
Texas Rangers v Seattle Mariners
woooooooooooo!
Photo by Steph Chambers/Getty Images

40 in 40: Bryan Woo is an unrefined gem

not 40 in 40: Bryan Woo, die lit

You’re all collectively welcome, fyi, for me not doing a stupid Whole Lotta Red/Die Lit bit with this article. I thought about it, and even started it, but I don’t even really like Playboi Carti, and the pun isn’t particularly good. Like, his Savant page has a lotta red. Yeah. Yawn. Shut up, Nick.

Anywho - it’s not an exaggeration to say Bryan Woo is one of the most exciting young arms in the league. His debut last season was highly-anticipated by prospect watchers, but perhaps went a little more under-the-radar than his rotation-mate Bryce Miller’s (the Bry-Guys, as they might be known).

Woo’s ascendance to the major leagues was so fast, in fact, he didn’t really have much time to hang out on any prospect lists. A 2021 6th-round draft pick out of Cal Poly, 2022 was his first season as a professional, and at the outset of the season, he wasn’t scratching any top-30 prospect lists.

Los Angeles Angels v Seattle Mariners
lookin’ up the prospect rankings at Yeury Tatiz and Jimmy Joyce
Photo by Steph Chambers/Getty Images

His results in 2022 also weren’t especially dominant. I covered High-A Everett for the site that year, where Woo was a mid-season call-up. His Everett numbers didn’t jump off the page: 7 starts, a 1-3 record and a 4.78 ERA don’t exactly scream “get this man to The Show!”

There were hints on the page of a great pitcher - looking under the hood, you can see a .375 BABIP plus a 3.47 FIP showing that he had some poor luck, and his 30+ K% shows a live arm with a knack for missing bats. Watching film at that time, though, I was struck by the difference between the results and how dominant he looked at times.

This is from Modesto, but man, would you look at the rise on that fastball? That thing goes crazy, and we’ll talk about it a little bit later.

After a promising if not overwhelming first year in the org, he spent the first half of 2023 ripping up Double-A Arkansas for all of 9 starts before he got the call.


The funny thing is, his story in his first season after the call-up was very similar. Woo’s results weren’t anything crazy last season - a league-average FIP, BB% and slightly above-average K% are impressive for a guy with less than 200 professional innings, to be sure, but not world-shaking. However, the results are betrayed by his Baseball Savant page, which shows Woo racking up a whole lotta red.

The thing that stands out to me right away here is the fastball Run Value. I’m a big fan of Run Value as a way to evaluate individual pitch’s effectiveness; I have a quick breakdown a few paragraphs down in last year’s 40 in 40 on Kirby. And, check it out - his fastball is a super productive pitch, generating a better RV/100 than Bryce Miller and Logan Gilbert’s well-regarded four-seamers.

It’s an unusual pitch. When I said earlier that it “rises” a lot, that was a bit of a lie. The interesting thing about that pitch is that the IVB is only 15” - good, but not anything eye-popping. What is eye-popping, though, is the VAA, or vertical approach angle. This is one of the flattest fastballs in the big leagues right now, due to the bonkers 4’11” release point he throws it from, while still generating that IVB. He’s a biomechanical marvel and should be studied in a lab.

This information, as well as a full, in-depth analysis of Woo’s pitches, can be found here by Jack Foley of Pitcherlist, a fantastic publication that I would recommend for all you pitching number perverts out there (you know who you are - you saw IVB and VAA and got all riled up). Really, if you care enough about Woo to be here now, you should check it out - it does a more exhaustive and better job of analyzing Woo’s arsenal than I can.

Long story short, arsenal-wise, he has three unique pitches - a low (high?)-VAA 4-seamer, a seam-shifted wake-y sinker, and a sweeper with a positive IVB (boi-oi-oi-oing, if you know what I mean), along with a gyro-cutter situation. He throws the fastballs about two-thirds of the time, and the gyro-cutter an additional 15% of the time, with the sweeper getting most of what’s left over.

For Woo to unlock the next level, more than a new pitch or tweak to an existing pitch, the first thing for him is the same story as many young pitchers: learning how to command his pitches. It’s not as though he lacks control - a lot of his pitches are able to find the strike zone often enough, and his BB% is perfectly average.

Where he struggles is throwing his pitches in an optimal spot for success. While his pitches are all good and unique, they aren’t so overpowering that he can throw them anywhere and have them dominate.

His fastball, with that artificial rise, needs to be thrown at the top of the zone for success.

Well, this is bad news for pretty much any fastball. And yet! It still is a successful pitch. Imagine how much value he’ll generate (and the whiffs!) once this is consistently thrown up high.

The sinker is actually already thrown in a great spot, which is probably part of why it has a slightly better RV/100 than the four-seamer (1.2 vs 0.9). The late movement generated by that seam-shifted wake, as well as hugging the edges, makes this pitch devastating. (Seam-shifted wake, or SSW, is a phenomenon that causes pitches to move differently than their spin tells the batter it should, by using the uneven seams on the ball to generate movement. For a deeper dive, check out this piece published by Driveline.)

It could probably afford to dive down a little bit further into the corner, but hey, this is an effective pitch.

The cutter has a pretty decent hotspot - it could possibly be more of a chase pitch out of the zone, but overall, it’s hitting a corner, which we love for it. The problem here is that while it does go to the right spot a decent amount of the time, it also goes all over the place - the overall zone here is much more Picasso compared to the other ones.

Speaking of abstract art:

Yeah, this might explain why the slider has a .321 BA and .571 SLG against. It’s not at all landing where you might want it to, or really, anywhere in particular at all. Compare this to a similarly-shaped pitch with much more success, Paul Sewald’s sweeper:

It’s a nice, tight band that takes advantage of the horizontal movement to either let it back-door into that outside edge against a leftie or to move all the way across the plate and make a right-handed hitter chase out of the zone.

Woo’s sweeper doesn’t rise quite as much as Sewald’s here, and might benefit from a tighter zone, but the concept is the same - use that sweeper that moves horizontally 74% more than average (5.7 inches more!) laterally to utilize the whole plate, and figure out a release point that works for him.


Woo has all of the tools to be a strong mid-rotation arm. One of the most exciting things about him is that he’s such a young pitcher, too - he only threw 70 innings in college! Including his professional innings and his summer ball innings up in the Alaska League, that’s only just over 300 innings since 2018, total. He’s still incredibly raw, but for Bryan Woo, raw still looks like being a serviceable major league starting pitcher. Just imagine what he’ll look like once he’s refined.

I think it’s fair to expect Woo to put up 2-3 WAR with a full season next year. If he can continue to evolve, he’ll be closer to 3-4 WAR kind of guy - a very strong mid-rotation starter with upside. If the Mariners are going to succeed with the shoestring budget they apparently must subsist on, Bryan Woo is the exact kind of player they need: young, cheap, and talented.

(PS: This didn’t fit anywhere in the article, but don’t forget that he gave us one of the most exciting defensive plays by a pitcher this season. Gold Glove Bryan Woo, anyone?)

Seattle Mariners Game Threads

Mariners 2024 Spring Training, Game # 1, 02/24/2024, SEA at CHW: Open Game Thread

40 in 40

40 in 40: J.P. Crawford keeps the Mariners on course

Mariners Moose Tracks, 2/24/24: Matt Brash, Brian Anderson, and Mike Ford