Bryan Woo is an Ace in the Making

An In-Depth Breakdown of Bryan Woo's Pitching Delivery, Its Impact on His Arsenal, and How He Can Take His Game to the Next Level

Feb 09, 2025

Opening

With spring training getting closer and closer, I'm going to continue my breakout players genre. I recently wrote about Spencer Arrighetti and the leap I believe he'll be able to take, but today, I want to look closer at one of my favorite pitchers: Bryan Woo. To some, Woo has already broken out, posting a great sophomore season with a 2.89 ERA, 2.72 xERA, and a 3.40 FIP over 121 and 1/3 innings pitched in 24’. But to other fans, Woo is practically unknown due to the insanely deep Mariners rotation consisting of Logan Gilbert, Luis Castillo, George Kirby, and Bryce Miller!

This sadly leads Woo to be labeled as the starting pitcher 5 of the rotation, but I assure you he's much more than that. The reason I believe Woo has the capability to take that next step towards becoming an ace is his deceptive release and use of angles to his advantage, as well as his effective secondary pitches. There are big things to come from Woo, who's just 25, so don't let the SP5 label fool you!

Delivery Characteristics

Before we get into the deceptive delivery characteristics, let's just take the time to appreciate how smooth of a delivery Woo has. He's extremely elastically efficient with his movements, which allow for effective use of the energy built up throughout his delivery and out into the throwing phase. Looking at Woo’s biases, it seems like he leans more so toward a supination bias with a bicep-dominant release. What I want to focus on, though, is Woo’s ability to get down to a well below-average release height of 5.1’ from a 6.2’ frame. This ability is a combination of his 6.8’ of extension and low slot arm angle of 27 degrees. What's great about this is how it allows him to use angles to his advantage on his fastball to make it practically unhittable. I'll touch on this more later, but it's one of the many reasons why I believe Woo has the capability to achieve ace status.

Effects on 4-Seam

Building off what I just said, Woo’s low release height is a major factor in why Woo’s pitches, especially his 4-seam, have the ability to be so good. The reason for this is because of how Woo is able to produce a -3.8 VAA on his 4-seam, which is one of the lowest in the leagues! This low VAA gives his fastball the illusion that it's almost rising when thrown at the upper thirds of the zone. That being so, it allows him to produce absurd results of a .225 xBA, .262 wOBA, .276 xwOBA, 27.3 Whiff%, and a 36.6% O-Sw% all together, and when targeted in the upper thirds, he was able to produce a .160 xBA, .210 wOBA, .210 xwOBA, and a 31.6 Whiff%!

Currently, Woo is targeting the upper thirds of the zone with his 4-seam 58.2% of the time, which is above average but could be viewed as too low with his VAA capabilities. I, for one, want him to play into this strength and target the upper thirds of the zone more to be the most effective version of himself. Overall, this is a great pitch that Woo leans on, throwing it over 49% of the time in 24’ and still being able to produce the great results above. This is just one of the many reasons I believe Woo has the ability to take the next step toward ace territory.

Arsenal

To add to his ability to produce such a great 4-seam, Woo also has a deep arsenal that can be effective vs. both-handedness. He mainly throws his 4-seam like I mentioned earlier, but Woo throws his sinker 23% of the time, slider 10% of the time, changeup 9% of the time, and sweeper 9% of the time. All of these pitches were very effective in their own respects, with his breaking pitches leading the way.

Woo only used these pitches (sweeper and slider) a total of 20% of the time combined, but they were arguably his most effective pitches. Starting off with his sweeper posting a .109 xAVG, .088 wOBA, .109 xwOBA, 41.7 Whiff%, and a 27.8 O-Sw%, while his slider was up there as well, posting a .227 xAVG, .346 wOBA, .247 xwOBA, 20.7 Whiff%, and a 38.0 O-Sw%. Some changes I could see to help take the next step toward “ace” territory are slightly increasing the usages of these pitches in place for his 4-seam and sinker usage, which I'll touch on next, but this would allow him to increase his unpredictability within his arsenal.

To hit on his other pitches, Woo’s sinker is very effective as well, posting a .244 xAVG, .255 wOBA, .271 xwOBA, 9.7 Whiff%, and a 22.2 O-Sw%. The only thing is that Woo uses this pitch vs. both-handedness, which generates the results you would expect. Against righties, he throws this pitch 30% of the time and was able to effectively produce a .226 xAVG, .214 wOBA, .247 xwOBA, and a 10.4 Whiff%. Against lefties, though, Woo threw this pitch 13% of the time, and it was much worse with a .274 xAVG, .327 wOBA, .313 xwOBA, and an 8.6 Whiff%. I could see the decreased use of the pitch against lefties in turn for his slider like I mentioned previously, or possibly a cutter, which I'll talk about later.

The final pitch within his arsenal is his changeup, which, like his other pitches, was great! In 2024, Woo was able to produce a .222 xAVG, .243 wOBA, .250 xwOBA, 20.7 Whiff%, and a 34.1 O-Sw%. I don't see major changes happening to this pitch because it does its part against lefties effectively. As many say, if it ain't broke, don't fix it.

Possible Addition

Now, Woo’s arsenal is great, as evidenced by his results, but I could see him possibly adding a cutter. Currently, Woo is slightly worse against opposite handedness, giving up a .222 AVG, .249 OBP, .356 SLG, and a .262 wOBA, while against righties, he's able to limit damage to a .200 AVG, .224 OBP, .316 SLG, and a .235 wOBA. The reason why Woo has differing splits is due to his limited/less effective attack against lefties, where he's predominantly throwing 4-seams, sliders, changeups, and sinkers. I think the addition of a cutter could replace the less effective sinker against lefties while also giving him another pitch-moving glove side that would allow him to get in on lefties. This possibility would allow him to take that next step towards becoming an "ace."

Conclusion

All in all, Bryan Woo is legit. He has the capability to be a top-of-the-rotation arm, but because the Mariners are so stacked, he's their SP5. One concern that has hindered Woo thus far in his career is his injury history. Woo has been on the IL three separate times in his short career with a multitude of injuries, which include forearm, elbow, and hamstring injuries. Despite this, when he’s healthy, he’s dominant! As I've shown in the article, he has a low release height with a dominant arsenal that could be improved with a cutter. These observations and facts lead me to believe that if Woo can stay healthy, he could become one of the game's next “aces.”