Giants 8, Padres 3: Buster Posey, Angel Pagan and Gregor Blanco each homered, and Matt Cain won his career-high sixth straight start as the Giants captured the rubber game of the three-game series.

Cain (7-2) gave up three unearned runs with nine strikeouts over seven innings to earn his first win over San Diego since Sept. 9, 2010. Santiago Casilla worked 1 1/3 innings for his 15th save.

The Giants scored twice in the first inning when Posey and Brandon Belt drove in runs off Jason Marquis (0-1), who was making his Padres debut after being released by the Twins on May 26.

San Francisco extended its lead with a run in the third before Posey hit a solo blast in the fourth. Marquis exited after giving up four runs (two earned) over six innings.

After Chase Headley capped the Padres’ three-run fifth inning with a two-run double, the Giants answered in the seventh when Pagan hit a two-run homer on a 3-2 pitch off Brad Brach.

Blanco, who homered for the second straight game in the eighth inning, went 7-for-15 in the series. The Giants added another run in the ninth when Pagan scored on Belt’s single.

San Diego, which has lost 15 of its last 20 games against the Giants, went 2-for-15 with runners in scoring position. Cameron Maybin went 0-for-5 and left eight runners on base.

GAME NOTEBOOK: Pagan went 2-for-5 to extend his hit streak to 15 games. … Cain improved his career record to 76-75. … The Giants committed four errors, and they lead the majors with 55 this season. …The Padres announced that Andrew Cashner will move from the bullpen and start Saturday against the Brewers. ...Reliever Ross Ohlendorf made his Padres debut in the ninth inning.