Sep 8, 2025; Seattle, Washington, USA; Seattle Mariners starting pitcher Bryan Woo (22) reacts after allowing a two-run home run to St. Louis Cardinals first baseman Alec Burleson (41, background) during the fourth inning at T-Mobile Park. Mandatory Credit: Joe Nicholson-Imagn Images Joe Nicholson-Imagn Images

Mariners' Pitching Staff Under Fire As Postseason Quickly Approaches

Originally posted on Fastball on SI | By Zach Pressnell | Last updated Sep 9, 2025 4:01 PM ET

The Seattle Mariners are clinging to the final American League postseason spot right now.

They've been one of the better teams in the AL for months, but they're seemingly falling apart with the season on the line. If the Mariners don't step up the production over the last few weeks, they could miss out on the postseason entirely.

Bleacher Report's Tim Kelly recently called the Mariners' pitching staff their fatal flaw for the postseason.

Mariners' pitching staff continues to struggle with postseason on the line

"In theory, the Mariners have as good of a starting rotation as anyone in baseball. But they are one of the teams we alluded to on the opening slide where the apparent strength of the team isn't performing like you would expect," Kelly wrote. "Since the All-Star break, Logan Gilbert has a 3.88 ERA. After missing nearly two months with right shoulder inflammation, George Kirby has a 4.47 ERA in 19 starts this season.

"Bryan Woo has been the ace for the Mariners this year, with the 25-year-old All-Star posting a 3.02 ERA over his first 27 starts of the season. But even with the success of Woo and a lineup that's as good as the M's have had in a long time, their success in the postseason, assuming they get there, is going to come down to their aces pitching like aces."

It's very shocking to see the Mariners' pitching staff struggle like this. They have three or four potential aces on their roster, but Woo is the only one pitching like it.

To make matters worse, this is the first time in the 2020s that the Mariners' offense has been as good as it is right now. Cal Raleigh is having one of the best seasons in franchise history. Julio Rodriguez has been excellent. Trade additions Eugenio Suárez and Josh Naylor could turn it up in the final few weeks.

But the Mariners need their pitching staff to pick up some of the slack. Woo can't be the only starter who pitches like an ace. That's not how the Mariners are built. They need their staff to be excellent, or the World Series is out of the picture.

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This article first appeared on Fastball on SI and was syndicated with permission.

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