Bryan Woo Won’t Fly Under the Radar in Seattle Much Longer

The Seattle Mariners have been known for the strength of their starting rotation for some time now.

In 2024, they were the co-leaders in team ERA alongside the Atlanta Braves. They also lead the league in WHIP and BAA, and were third in FIP.

In 2023, it was much of the same. They sat third in ERA, second in both FIP and WHIP and seventh in BAA.

A lot of the shine goes to the trio of Logan Gilbert, George Kirby and Luis Castillo. Gilbert’s a 2024 All-Star who’s tossed three consecutive sub-4.00 ERA campaigns entering 2025. Like Gilbert, Kirby has also been a consistent sub-4.00 ERA, All-Star caliber arm. Then there’s Castillo, and wouldn’t you believe it, he too has been a sub-4.00 ERA All-Star arm since joining the Mariners in the middle of the 2022 campaign.

Now, 2025 hasn’t necessarily gone to plan with the Mariners staff, largely due to injuries to both Kirby and Gilbert, as they sit 15th in ERA and FIP, 20th in WHIP and 24th in BAA.

That being said, amidst a rockier start than normal and key injuries to the heart of this rotation in Gilbert and Kirby, there’s been one name in particular in Bryan Woo who’s stepped up and proven his weight in gold by leading this unit.

And as a result, the Mariners entered the month of June 0.5 games up on the Houston Astros for first in the AL West, with a 32-26 record.

Bryan Woo has Been the Mariners Rotation’s Secret Weapon

Woo has been extraordinary to start the 2025 campaign. In 70.1 innings pitched across eleven starts, Woo has thrown to a 2.82 ERA, 3.06 FIP, 0.95 WHIP and .219 BAA.

This, however, has not been the first time Woo has dazzled on the mound. Even though eyes may have been on the formidable trio of Gilbert, Kirby and Castillo, he’s also coming off a year where he threw to a 2.89 ERA, 3.40 FIP, 0.90 WHIP .211 BAA in 121.1 innings pitched across 22 starts.

Naturally it makes sense for Mariners fans to gravitate towards the three big All-Star names at the top of their rotation. After all, they’ve been one of if not the most integral part of putting the Mariners back on the competitive map after such a long hiatus from meaningful baseball.

However, that shouldn’t diminish anything Woo has done to this point, as he may fly under the radar now but there’s no reason for him to continue to fly under the radar of most baseball fans.

Woo is on a crash course for All-Star consideration this season, just like the majority of his fellow rotation mates have received in the past.

Not only do his stats both this year and last year paint a great picture of what Woo can offer this Seattle team, but his underlying metrics paint a picture of sustainable success.

Looking at his dominant run so far in 2025, he’s limiting the amount of quality contact made against him with a 71st percentile hard hit rate of 37.1% and a 78th percentile AVG exit velocity that sits at 87.9%, according to Baseball Savant.

He’s also been elite at limiting walks with a 98th percentile BB% of 3.3% and manages to induce an above average 65th percentile clip of 29.5% when it comes to getting opposing hitters to chase.

Pair all of this with an impressive 77th percentile 3.10 xERA and it looks clearer and clearer that Woo is the real deal.

Then, when looking at his pitch mix and how hitters have managed to struggle against two of his main offerings tells the same story. Woo throws his four seam fastball 42% of the time and only sports a .184 BAA and .367 SLG. His slider (used 12.6% of the time) is his third most commonly used pitch and has held hitters to a .111  BAA and .111 SLG.

From a broader perspective these underlying metrics like these have made Woo into one of the league’s brightest starting pitchers. Dating back to the start of last season, amongst pictures with at least 150 innings pitched, Woo sits in the Top 10 in ERA (10th at 2.87) and WHIP (3rd at 0.92), and sits amongst the Top 20 in FIP (19th at 3.27) and BAA (15th at .214).

Woo’s fellow rotation mates aren’t the only reason he falls outside of the household name threshold. It’s also due the fact that he doesn’t excel in certain attributes commonly associated with memorable pitchers, such as striking hitters out (55th percentile K-rate and 36th percentile whiff rate) or keeping the ball on the ground (35th percentile ground ball rate). This makes it a little easier to see why Woo hasn’t received the fanfare that someone with his stat line should be receiving.

Pitching aside, Woo also has to compete with the likes of offensive stars like Julio Rodriguez and Cal Raleigh for time in the spotlight as well.

All that to say, the Mariners only have two qualified starters this season, him and Castillo, and he’s comfortably pacing his counterpart across the board.

He may not have the benefit of first round pedigree like Gilbert or Kirby, or the recognition that nearly a decade of sustained big league success will get you like Castillo has, but there’s no arguing that what Woo is doing is not impressive.

Should the Mariners find a way to continue their early success in 2025 and return to the postseason for the first time since 2022, and Woo is able to continue to do what he’s been doing for over year now, then it will go a long way into elevating him into everyday conversations about the league’s best starting pitchers.