Sep 13, 2025; Seattle, Washington, USA; Seattle Mariners starting pitcher Bryan Woo (22) pitches to the Los Angeles Angels during the first inning at T-Mobile Park. Mandatory Credit: Steven Bisig-Imagn Images Steven Bisig-Imagn Images

Seattle Starter Bryan Woo Listed as Day-to-Day with Muscle Tightness

Originally posted on Seattle Mariners on SI
By Ryan Boman | Last updated Sep 21, 2025 12:58 PM ET

In his last start, Mariners righthander Bryan Woo had everything working for five scoreless innings against the Houston Astros on Friday night. But by the sixth, tightness in his pectoral muscle forced the 25-year-old hurler to inform the medical staff that something wasn't quite right

“I felt great all game, just felt it at the end, and, yeah, just felt it was smart to not try and push it,” Woo said.

Despite the roadblock for Woo, the bullpen chipped in to pitch a shutout, 4-0 over Houston, with the starter still picking up the victory. That moved Woo's record to 15-7, with an ERA of 2.94 and 198 strikeouts in his 30 starts this season.

“You’re obviously concerned in some ways, but in other ways, Bryan, he’s a tough cookie,” Mariners manager Dan Wilson said after Friday's win. “It was smart that he let us know, and there was no reason to push it. We’ll find out more tomorrow.”

What's the Pitcher's Prognosis?

Joe Nicholson-Imagn Images

For now, it appears that the Mariners are hoping that rest will be enough to help Woo's pectoral heal. They don't anticipate the ace pitcher to be forced to go on the Injured List. His next scheduled start was set for Seattle's home series against the Colorado Rockies.

However, that date isn't firm, and will be contingent on not only Woo's health, but where the Mariners are at in terms of the postseason at that point. If it's deemed that there's no reason to trick anything with their most reliable moundsmen, he could be held out until the playoffs. As for now, nothing is written in stone, according to the club's skipper.

“It’s really just kind of a day-to-day thing,” Wilson said. “We'll continue to assess it each day. We'll know a little bit more in the next 24-48 hours, depending on how he responds. And that's really what we know at this point... He has put together an incredible season in terms of his health and being healthy all season long."