The Royals remained five games behind Toronto for the second Wild Card spot in the American League. The Royals, who have just 17 games left, have lost three straight overall, and they've lost seven of their last eight at home.
A's left-hander Sean Manaea, a former Royals prospect, breezed through five innings in his first start since Aug. 29. Manaea, who had been rehabbing a back injury, gave up three hits and struck out five.
Yonder Alonso and Marcus Semien each had two-run doubles for the A's.
Royals right-hander Yordano Ventura struggled with his command, throwing just 58 strikes out of 100 pitches.