SEATTLE -- Matt Olson hit a grand slam that capped a six-run fifth inning, Khris Davis added his major league-leading 47th home run and the Oakland Athletics beat the Seattle Mariners 9-3 on Wednesday night to close on the New York Yankees for home-field advantage in next week's AL wild-card game.
With the score 3-3, Nick Martini hit an RBI single that chased Felix Hernandez (8-14), who made his first appearance since gaining American citizenship this week. Marcus Semien added a run-scoring single against Chasen Bradford before Olson's drive to right-center.
Oakland (96-63) improved to a big league-best 41-21 since the All-Star break and trails the Yankees (97-61) by 1 1/2 games. New York holds the tiebreaker to host the Oct. 3 game; the wild-card winner advances to the Division Series against AL East champion Boston.
Chad Pinder also homered for the A's, who reached 96 wins for the first time since 2013.
Ryan Buchter (6-0) pitched a hitless inning in relief of Edwin Jackson who gave up three runs and five hits in 4 1/3 innings.
Hernandez, a 32-year-old Venezuelan who won the 2010 AL Cy Young Award, was sworn in as a U.S. citizen on Monday. He gave up five runs - four earned - three hits and two walks, and finished with a 5.55 ERA, more than a run above his previous career-high last year. His ERA has more than doubled since he led the AL in 2014 at 2.14.