Mariners vs. Tigers: Bryan Woo left off Seattle's ALDS roster, per report
Seattle and Detroit open their series on Saturday night

The Seattle Mariners will be without ace Bryan Woo when they begin their best-of-five American League Division Series against the Detroit Tigers on Saturday night, according to Adam Jude of the Seattle Times. Woo has been sidelined since Sept. 19 after experiencing inflammation in his pectoral muscle. He threw a bullpen session just a few days ago, but even then, he conceded he wasn't quite where he needed to be to take part in a competitive game.
"A positive day," Woo said on Thursday. "I'm still not where I want to be in terms of game speed of everything, but in terms of how everything's progressed, [I'm] happy with it, considering a week ago I wasn't even throwing yet. And then a week from now, hopefully, we'll be in a better spot."
Woo, 25, had a standout season for the Mariners. In 30 starts, he compiled a 2.94 ERA (128 ERA+) and a 5.50 strikeout-to-walk ratio. He averaged more than six innings per appearance and was named to his first career All-Star Game earlier this summer. Unfortunately, Woo will have to wait before he's able to celebrate his first career postseason pitching appearance.

The Mariners' playoff rotation will certainly include George Kirby, Logan Gilbert, and Luis Castillo. The question, then, is who the Mariners use as their fourth starter. Bryce Miller, Emerson Hancock, and Logan Evans are the most obvious candidates, though each has their flaws.
The Mariners have an incentive to err on the side of caution with Woo -- because of his health and long-term importance to the franchise, but also because of how roster moves work in the postseason. Teams are not allowed to add and subtract freely. They must set their rosters in advance of a round and stick to them. If a player must be removed because of injury, they're ineligible to partake in the subsequent series. In this case, if Woo required a substitute, he then would've been unable to participate in the League Championship Series.
The Mariners and Tigers will get underway at 8:38 pm ET.