Seattle Mariners pitcher Bryan Woo. Erik Williams-Imagn Images

SP Bryan Woo's absence could be hard for Mariners to overcome

By Eric Smithling | Last updated Oct 4, 2025 3:38 PM ET

The Seattle Mariners have already received a blow before their postseason even begins.

On Saturday, the team kept starting pitcher Bryan Woo, the ace on its staff, off its ALDS roster, increasing the degree of difficulty heading into the best-of-five series against the AL wild-card Detroit Tigers (87-75).

The Mariners (90-72) managed to complete their comeback to win the AL West without Woo, but advancing to the ALCS for the first time since 2001 will be difficult with their best pitcher.

Mariners rotation has uneven history against Detroit Tigers

Saturday's Game 1 starter, George Kirby, has struggled historically against the Tigers, going 2-4 in six previous starts with a 7.48 earned run average (ERA). Kirby has allowed 23 earned runs and 40 hits with 32 strikeouts in 27.2 innings. In his most recent start this past July 12, Kirby allowed nine base runners in 23 batters, giving up four earned runs in a 15-7 win, via Stathead.

A big blow for the Mariners as Bryan Woo has been left off their ALDS roster pic.twitter.com/ocfhuBYwhG
— Talkin’ Baseball (@TalkinBaseball_) October 4, 2025

Luis Castillo, slated to start Game 2, has fared better against the Tigers, recording a 3.95 ERA in seven career starts. But he's scheduled to start opposite Detroit ace Tarik Skubal, the AL's most dominant pitcher, meaning he won't have any margin for error before the series heads to the Motor City for Game 3 and, if necessary, Game 4.

During the season's second half, the Mariners had one of the best bullpens in the majors, ranking eighth in reliever ERA (3.67) and fourth in relief pitching wins above replacement, or WAR (2.7), per FanGraphs data. One of the keys of the series could be how quickly the Tigers force Mariners manager Dan Wilson to dig into his bullpen. If he has to turn to his relievers early, that could be a boost for Detroit the longer the series goes.

Seattle will need its starters to eat up meaningful innings to keep the relief staff fresh. Without Woo, that will be much more difficult.

Eric Smithling

Eric Smithling is a writer based in New Orleans, LA, whose byline also appears on Athlon Sports. He has been with Yardbarker since September 2022, primarily covering the NFL and college football, but also the NBA, WNBA, men’s and women’s college basketball, NHL, tennis and golf. He holds a film studies degree from the University of New Orleans

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