Mike Yastrzemski and Patrick Bailey homered and Michael Conforto added four hits and three RBI to pace a balanced attack to help the Giants beat the Cardinals 11-3.
Yastrzemski and Bailey hit back-to-back homers in the sixth to push the lead to 9-2.
Jack Flaherty worked only 4 1/3 innings, gave up 6 runs on 10 hits and walked 3.
Keaton Winn’s first trip to a major league ballpark also became the site of his first big league save.
Winn worked four solid innings of relief. Winn allowed one run on one hit in a 55-pitch effort and was doused with a combination of hot sauce and toothpaste by his teammates after the contest.
San Francisco outfielder Mitch Haniger suffered a fractured right forearm after being hit by a pitch from Jack Flaherty in the third inning.
LHP Jordan Montgomery (3-7, 3.88) will go for St. Louis in the finale of the three-game set on Wednesday afternoon, 11:20 with the pregame and the first pitch at 12:15 on KIRX.