Sean Manaea and two relievers shut down the Seattle bats, and Jed Lowrie's two-run homer was all Oakland would need to beat the Mariners 2-1 Sunday at Safeco Field.
The Mariners (8-5) took two out of three games with Oakland (6-10), and now face World Series champ Houston in a four-game series, starting at 7 p.m. Monday. James Paxton pitches opposite Dallas Keuchel.
The Astros are 10-6 and second behind the Los Angeles Angeles (13-3), who have won seven consecutive games, in the American League West Division. Seattle is third.
The Astros have lost consecutive games, including 3-1 to Texas on Sunday when ageless pitcher Bartolo Colon took a perfect game into the eighth inning.
Lowrie stroked his two-run homer off Felix Hernandez, who pitched well, giving up five hits and two runs while striking out seven and walking none in 6 1/3 innings.
But Manaea was just better. He gave up two hits and one run, on Taylor Motter's fifth-inning solo homer, and struck out four and walked two in seven innings. Ryan Buchter and Blake Treinen pitched hitless innings in relief.
Kyle Seager had a single for Seattle's only other hit.