SEATTLE -- Pinch-hitter Chris Herrmann's two-run homer in the 11th inning gave the Seattle Mariners a 10-8 win over Oakland on Tuesday night, clinching the AL West for Houston and leaving the Athletics with a wild-card matchup against the New York Yankees.
Seattle overcame an 8-5 eighth-inning deficit and dropped the A's 2 1/2 games behind the Yankees for home-field advantage in the Oct. 3 winner-take-all matchup. Oakland had been 68-0 when leading after seven innings.
Denard Span hit a two-run double off Fernando Rodney in the eighth.
Blake Treinen was one strike from closing out his 38th save in the ninth, but Nelson Cruz punched a two-out single, Ryon Healy reached when third baseman Matt Chapman bobbled his grounder for an error and Kyle Seager hit an RBI single. Treinen had allowed just one hit in his previous 13 appearances.
Ben Gamel walked with one out in the 11th against Emilio Pagan (3-1), and Herrmann batted for Andrew Romine and sent an 0-1 fastball out to deep right-center field.
Alex Colome (7-5) pitched the 11th for the victory.
A day after clinching no worse than a wild-card berth, Oakland took a 6-3 lead in the first two innings off Mike Leake. Nick Martini had a two-run triple and Matt Joyce a two-run single off Leake, and Marcus Semien added his 14th home run leading off the fifth inning. But the A's went scoreless after Matt Olson's RBI double in the sixth inning.
Edwin Diaz, the major league leader in saves, pitched the 10th for Seattle. Diaz had not pitched since Sept. 17, when he collected his 56th save.
Oakland manager Bob Melvin said the priority in the coming days will be making sure the A's regulars get a chance at some rest so they are fresh when the postseason begins. Melvin indicated getting his guys rest would take priority over trying to chase down the Yankees in an attempt to have the wild(equals)card game at home and not in New York. The A's gave Khris Davis and Stephen Piscotty the night off on Tuesday.
"There is definitely a balance to this but I think the depth of our team allows us to be confident with who we give a day off to, whether it's in the lineup or in the bullpen," Melvin said. "But it is important at this point if time in the season that once we get to the postseason that guys are fresh. It's just as much of a mental grind as it is a physical grind too. One of the strengths of our team is we use all our guys."
The one guy that may not get any rest is Matt Olson, who has a chance at playing in 162 games. Melvin said he probably won't start Olson at least one game against the Angels this weekend but will do what he can to make sure Olson reaches his goal of playing in every regular season game.
As for pitching, Melvin said the staff hasn't figured out who would pitch this weekend against the Angels, let alone in a wild card game.
"We're leaving everything open," Melvin said.
Athletics: RHP Edwin Jackson (6-3) makes his 17th start since joining the A's on June 25. Jackson has a 3.18 ERA in his 16 starts, the fourth lowest in the American League during that stretch.
Mariners: RHP Felix Hernandez (8-13) makes what is likely his last start of the season. Hernandez will finish the year with a career-worst ERA (currently 5.46) and the 13 losses are one shy of his career-high.