Oakland helped itself by turning a team record-tying five groundball double plays, and stopped a five-game home skid.
The A's scored four times in the first inning, two on Piscotty's double off Hernandez (5-4). Hernandez settled down and retired 16 of the last 17 batters he faced in going six innings.
Yusmeiro Petit (2-1) pitched three scoreless innings in relief. He was among five A's pitchers manager Bob Melvin used after saying it would be a bullpen day with rookie reliever Josh Lucas making a spot start.
Lucas lasted just two innings in his first career start, allowing two runs on three hits and three walks and throwing 52 pitches. The Mariners loaded the bases with no outs in the first, but managed just one run as Nelson Cruz grounded into a double play and Kyle Seager struck out.
Seager hit an RBI double off Blake Treinen in the eighth. Treinen got Daniel Vogelbach to fly out to end the inning with runners at second and third, and worked the ninth for his 11th save.
Jed Lowrie hit a sacrifice fly in the first, Piscotty doubled and Dustin Fowler had an RBI single.
Mariners: OF Mitch Haniger, who sat out Wednesday's game after being hit by a pitch on his right forearm the previous day, was back in the lineup.
Athletics: LHP Ryan Buchter (strained left shoulder) threw on flat ground from 75 feet on Thursday without discomfort. Melvin said the team doesn't have a timetable for when he'll throw off a mound, the next step in his recovery. . RHP Liam Hendriks (strained right groin) left for Arizona on Thursday to pitch in extended spring training games, Melvin said. . RHP Paul Blackburn (strained right forearm) is headed to Arizona, too, and could soon start a rehab assignment.
Mariners: LHP James Paxton (3-1, 3.30 ERA) will pitch in Friday's series opener against Minnesota. Paxton is 2-1 with a 2.91 in three career starts against the Twins.
Athletics: LHP Sean Manaea (5-4, 2.71) will pitch Friday's series opener against Arizona. Manaea has never faced Arizona but is 2-4 with a 3.63 ERA in eight career interleague starts.
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