Cruz's fifth-inning blast to center field snapped a 1-1 tie and gave the Mariners the victory in the opener of the three-game series at Safeco Field.
Hernandez (4-2) allowed three runs on three hits in six-plus innings, with two of the runs scoring after he exited. Hernandez walked four and struck out seven.
Trailing 5-1, the A's scored twice in the seventh. Khris Davis, who has three home runs in six previous games against Seattle this season, led off with a walk. He moved to third on Matt Olson's double to right field.
That was all for King Felix, who was replaced by Nick Vincent.
Vincent caught Matt Chapman on a called third strike for the first out of the inning. Mark Canha then hit a ball up the middle that deflected off Vincent's glove and rolled behind shortstop Jean Segura, who broke behind second base to where the ball was headed before Vincent touched it.
By the time Segura chased it down, he had no play, with Davis scoring and Olson moving to third.
Chad Pinder brought home Olson on a groundout to first, but Vincent struck out Jonathan Lucroy to end the inning with the Mariners holding a 5-3 lead.
Seattle's Juan Nicasio pitched a perfect eighth, striking out two, for his major-league leading 11th hold, and Edwin Diaz worked the ninth for his MLB-best 12th save, also striking out two.
The A's opened the scoring in the top of the first as Jed Lowrie hit a solo homer to right-center field on a 2-2 pitch. Lowrie's seventh homer of the season came after Hernandez struck out the first two batters.
The Mariners tied it in the second as Kyle Seager led off with a ground-rule double to right-center. Seager moved to third on Mitch Haniger's flyout to right and scored when Mike Zunino doubled to left.
In the bottom of the fifth, Dee Gordon reached on an infield single, one of his five hits on the night, and advanced to second on a wild pitch by right-hander Andrew Triggs. After a walk to Segura, Robinson Cano flew out to the wall in the deepest part of center field.
Cruz hit the next pitch for his sixth homer of the season.
Triggs (2-1) allowed four runs on six hits in 4 2/3 innings. He walked three and struck out four.
--Field Level Media
Oakland | Seattle | |
Andrew Triggs | Player | Felix Hernandez |
Loss | W/L | Win |
4.2 | IP | 6.0 |
4 | Strikeouts | 7 |
6 | Hits | 3 |
7.71 | ERA | 4.50 |
Oakland | Seattle | |
Matt Olson | Player | Dee Gordon |
1 | Hits | 5 |
0 | RBI | 0 |
0 | HR | 0 |
2 | TB | 6 |
.500 | Avg | 1.000 |