Padres 6, Giants 3: Jason Marquis pitched 7 1/3 solid innings, Jesus Guzman homered twice and Chase Headley hit a solo shot as visiting San Diego unloaded on Tim Lincecum.

Will Venable added a two-run double for the Padres, who won for only the third time in their last 13 games at San Francisco in salvaging the finale of the three-game series.

Lincecum (4-11), who had allowed only two runs in two outings since the All-Star break, yielded five runs, seven hits and struck out eight in 4 2/3 innings as the Giants fell to 6-17 in his 23 starts this season. Lincecum’s National League-worst ERA swelled to 5.88.

Marquis (4-5), who won his third straight game, allowed three runs (one earned), three hits and struck out eight. He yielded a leadoff single to Gregor Blanco, then didn't allow another hit until Angel Pagan ripped a two-out double in the seventh. He retired 17 straight batters at one point.

Headley matched his career high of 12 homers with a solo shot to center field with two outs in the first inning. Melky Cabrera tied it in the bottom half with a sacrifice fly.

San Diego took a 3-1 lead in the third inning when Venable doubled into the left-center field gap to score Guzman and John Baker, who reached with singles.

Guzman’s two-run blast with two outs in the fifth inning made it 5-1 and he completed his first two-homer game with a solo shot in the eighth inning off Brad Penny to increase San Diego’s lead to 6-1.

The Giants scored twice in the eighth when Brandon Belt scored on Marquis’ wild pitch and Ryan Theriot delivered a two-out, two-strike RBI single off reliever Luke Gregerson.

Closer Huston Street came on to strike out Cabrera with two on to end the eighth inning and pitched the ninth to earn his 17th save in 17 chances.

GAME NOTEBOOK: Giants 3B/1B Pablo Sandoval did not play Wednesday after an MRI revealed a left hamstring strain. He suffered the injury while doing the splits to complete a double play while playing first base Tuesday. With an off day Thursday, manager Bruce Bochy said the team will wait until Friday to decide whether to place Sandoval on the disabled list. … Lincecum, who fell to 10-5 lifetime against San Diego, has 25 strikeouts in 19 2/3 innings since the All-Star break. … The Giants are 9-3 since the break; the Padres 8-5. … San Diego rookie 1B Yonder Alonso went 0-for-4 and is hitless in his last 20 at-bats. … The Padres are 6-17 in their last 23 games against the Giants.