The A’s only scored twice off Hernandez (10-5) but peppered him for 10 hits – the most he has allowed this season.
Hernandez, who struck out six and walked two, had gone 13 consecutive starts without losing at the Coliseum, matching the longest streak by an opposing pitcher. The loss – his first in Oakland since Sept. 19, 2008 – was just his third in 21 career starts at this aging facility.
Graveman (6-4) allowed five hits to earn his third straight win.
Drew Pomeranz pitched the eighth and Tyler Clippard worked the ninth for his 15th save to complete the six-hit shutout.
Billy Burns singled twice, Ben Zobrist drove in two runs and Stephen Vogt added two hits for the A’s. Oakland had not beaten Hernandez at all since Sept. 27, 2013, but jumped on the 2010 AL Cy Young winner early.
Burns singled on the first pitch Hernandez threw then stole second. After Hernandez walked Vogt, Zobrist singled to drive in the A’s first run.
Oakland had runners at the corners with two outs later in the inning but failed to add on when Vogt was thrown out at home as part of a double-steal attempt.
Hernandez worked out of another jam in the second after the A’s loaded the bases with no outs. Marcus Semien struck out swinging, Burns flied out to shallow center and Vogt grounded out.
Graveman was just as good when he retired three straight after giving up consecutive singles to Robinson Cano and Nelson Cruz in the seventh. One of those outs came when Graveman made a stellar play to grab first baseman Ike Davis’ toss to get Seth Smith at first after Davis made a diving stop.
The A’s added an insurance run in the seventh. Burns singled and scored on a sacrifice fly by Zobrist.
Mariners: OF James Jones, RHP Mayckol Guaipe and LHP Davis Rollins were all called up from Triple-A Tacoma before the game. LHP Roenis Elias, who took the loss on Friday, was sent down along with LHP Vidal Nuno and RHP Tom Wilhelmsen.
Athletics: RHP Sonny Gray threw off a mound for the first time since being hospitalized with salmonella and could start Tuesday’s road opener against the New York Yankees.
Mariners: LHP Mike Montgomery (3-2) carries an 18-inning scoreless streak into Sunday’s series finale and will attempt to become just the second pitcher in franchise history to throw three consecutive shutouts. Hall of Famer Randy Johnson did it in 1994.
Athletics: RHP Chris Bassitt (0-1) will make his second straight start in place of Gray.