Mike Yastrzemski launched a two-run homer with one out in the bottom of the 10th inning Wednesday afternoon, allowing the San Francisco Giants to walk off the visiting Cincinnati Reds for an 8-6 victory and avoid a three-game sweep.

After Erik Miller (1-0) had stranded extra-inning courtesy runner Noelvi Marte at third base in the top of the 10th, Heliot Ramos’ leadoff flyball advanced Giants runner Matt Chapman to third.

Needing just a sacrifice fly to end the game, Yastrzemski did one better, belting a shot off Emilio Pagan (0-1) over the right field wall for his second home run of the season and the Giants’ third walk-off.

San Francisco’s Wilmer Flores set the stage for the dramatic finish with a leadoff home run in the bottom of the eighth, his fifth of the season, off the Reds’ fourth pitcher, Tony Santillan, drawing the hosts even at 6-6.

After prevailing in a pair of pitchers’ duels to open the series, the Reds used a five-run third inning against Giants starter Justin Verlander to go up 6-1. Elly De La Cruz had a two-run double and Gavin Lux a two-RBI single in the uprising.

Verlander was pulled after 5 2/3 innings, charged with six runs (five earned) on five hits and three walks. He struck out nine.

The Giants erased most of their deficit in a four-run sixth that spelled the end for Reds starter Nick Martinez. Flores and Tyler Fitzgerald had RBI singles in the rally, sandwiching a run-scoring triple by Patrick Bailey.

Like his counterpart, Martinez lasted just 5 2/3 innings, during which he allowed four runs and seven hits. He walked one and struck out eight.

Flores had two singles to go with his home run, scored twice and drove in two runs for the Giants, who improved to 2-0 in extra innings.

Jung Hoo Lee had a single, double and triple for San Francisco, while Yastrzemski, Bailey and Fitzgerald collected two hits apiece in a 12-hit attack.

De La Cruz had two of the six hits for the Reds, who played their first extra-inning game of the season.