Semien's first career walk-off hit off right-hander Noe Ramirez (0-1), the Angels' seventh pitcher of the day, came after the A's, down 4-0 and 5-4, had twice rallied to tie the game, the last time on a run-scoring single in the seventh inning by Khris Davis, his fourth RBI of the game.

The game featured the Major League Baseball debut of Japanese star Shohei Ohtani, who recorded his first MLB hit in his first at-bat. Ohtani, scheduled to make his pitching debut as the starter in Sunday's series finale, grounded the first pitch he saw from A's right-hander Kendall Graveman into right field in the second inning.

The left-handed hitter finished 1-for-5, grounding out in three consecutive at-bats before striking out against winner Chris Hatcher (1-0), the fifth A's pitcher, in the top of the 11th.

Ohtani's single came as part of a two-run second inning that gave the Angels an early lead. He appeared headed for the first run of his MLB career when Martin Maldonado hit a shot to the gap in left-center field, but when the ball one-hopped the fence for a ground-rule double, scoring Kole Calhoun, the speedy Ohtani was held to third base. He was stranded there when Zack Cozart flied out.

Calhoun and Cozart each hit solo homers, giving the Angels a 4-0 lead into the bottom of the fifth. But the A's countered with back-to-back homers by Davis, a three-run shot, and Matt Olson to forge a 4-all tie in the fifth.

Albert Pujols added a third Angels solo homer, the 615th of his career, leading off the sixth for a 5-4 lead. But again the A's drew even, this time on Davis' single that scored Semien in the seventh.

Neither starting pitcher got a decision, both pitching five innings.

Angels right-hander Garrett Richards took a shutout two outs into the fifth inning before giving up the home runs to Davis and Olson.

He was replaced after the inning, having allowed four runs and seven hits. He walked three and struck out four.

Graveman, who beat the Angels on Opening Day last year, was pulled after surrendering Pujols' homer leading off the sixth. He was charged with five runs on seven hits. He struck out one and did not walk a batter.

Semien had three hits, while Jed Lowrie, Davis and Powell (double, triple) collected two apiece for the A's, who were out-hit 13-12.

Cozart, Calhoun and Maldonado had three hits apiece for the Angels, while Pujols added two.

Mike Trout went 0-for-6, stranding two runners with an inning-ending strikeout against Hatcher in the top of the 11th.

--Field Level Media