Matt Chapman, Jerar Encarnacion and Luis Matos each homered in a six-run fourth inning Sunday as the visiting San Francisco Giants squeaked past the San Diego Padres 7-6.

Erik Miller (4-5) pitched 1 2/3 scoreless innings out of the bullpen to get the win after starter Spencer Bivens was hooked two outs shy of qualifying for the win. Bivens gave up four hits and a run in 4 1/3 innings with a walk and three strikeouts as San Francisco (71-73) took two of three from its National League West rival.

Joe Musgrove (5-5) was knocked out after 4 1/3 innings in his first bad start since coming off the injured list Aug. 12. Musgrove gave up six runs on eight hits and a walk, striking out seven, as San Diego dropped to 81-64.

The Padres’ lead on Arizona for the NL’s first wild-card spot fell to one game, pending the outcome of the Diamondbacks’ game Sunday night in Houston. San Diego dropped six games behind Los Angeles in the NL West after the Dodgers’ 4-0 win over Cleveland.

Musgrove, who allowed just four runs in his first five starts off the injured list, cruised through three innings before the home run ball bit him in the fourth. Chapman broke a scoreless tie with a two-run blast, his 23rd of the year.

Encarnacion followed with a three-run shot, his third, and Matos lined a solo shot to left for his fifth homer. The Giants’ other run came in the seventh via Curt Casali’s first homer of the season.

That made it 7-1 and turned out to be vital when San Diego mounted a late rally against the bullpen. Tyler Rogers wild-pitched Jackson Merrill home with the bases loaded in the seventh, followed by Tyler Fitzgerald dropping Jurickson Profar’s pop-up in short right-center field to score two runs.

Xander Bogaerts drilled a two-run homer, his ninth of the year, to left field in the eighth to make it a one-run game. Ryan Walker got the last five outs for his seventh save.

Merrill’s 23rd homer of the year in the fifth was the only run the Padres managed off Bivens.