SAN DIEGO -- One of the last decisions San Francisco Giants manager Bruce Bochy has to make is his starting rotation for the playoffs.

Madison Bumgarner probably will be in the rotation, despite having some struggles since the end of August.

Bumgarner lost 7-3 to San Diego on Saturday night, when Chase Headley hit his 30th home run and had three RBI to tie Milwaukee's Ryan Braun for the NL lead with 112.

Bumgarner said he struggled with his mechanics.

"We definitely have some time to work on it," he said. "I'm not worried about anything. I have to be able to make pitches when it counts."

He said his confidence is good. "I'm not worried," he said.

"Like anybody, he's gone through a little rut here. He pitched well last start but today he was really fighting himself out there," said Bochy, whose Giants clinched the NL West title a week ago with an 8-4 home victory over San Diego.

Bumgarner (16-11) allowed five runs, four earned, and four hits in four innings. He struck out four and walked two. Bumgarner had won his last four decisions against San Diego, including going 3-0 with a 3.08 ERA in four previous starts against the Padres this season.

"The problem may be I'm thinking about it instead of just going out there and throwing it," Bumgarner said.

San Francisco's Buster Posey, who started at catcher a night after being hit in the throat with a wild pitch, went 2 for 2 with a to raise his average to .337 and increase his lead in the NL batting race over Pittsburgh's Andrew McCutchen. McCutcheon went 1 for 5 to drop to .329. Suspended outfielder Melky Cabrera of the Giants has a .346 mark but won't qualify for the batting crown at his own request after a positive drug test.

Headley hit a two-run homer off Madison Bumgarner in the third to give the Padres a 4-3 lead. It's San Diego's first 30-homer season since Adrian Gonzalez had 31 in 2010, and the 17th time it's been done in team history. Headley also had an RBI grounder in the first and scored three runs.

The Padres scored as many runs Saturday night as they did in being outscored 19-7 during a three-game losing streak. Chris Denorfia had three hits and scored twice.

San Francisco's Hunter Pence hit a three-run homer off Eric Stults in the first, his 23rd. Pablo Sandoval was aboard on a walk and Posey on a single, both with two outs. Center fielder Cameron Maybin then made a spectacular leaping catch to rob Xavier Nady of a home run.

San Diego got two runs back in the bottom of the first on Headley's RBI grounder and Yasmani Grandal's sacrifice fly.

Jesus Guzman and Grandal each drove in two runs for the Padres. Guzman hit a solo homer with two outs in the third and an RBI double in the fifth. Grandal hit an RBI single in the fifth.

Stults (8-3) allowed three runs and six hits in six innings, struck out five and walked three.

San Francisco's Marco Scutaro singled in the fifth to extend his hitting streak to a career-high 17 games, the longest active streak in the majors.

Notes

Posey was replaced by Eli Whiteside starting the bottom of the sixth. Giants manager Bruce Bochy said Posey was sore and his voice was raspy after being shaken up Friday night when a pitch from Ryan Vogelsong bounced in the dirt, ricocheted up and hit right underneath his hockey-style catcher's mask. Bochy said Posey is scheduled to have Sunday off, as are a number of other players. ... The series concludes Sunday when Tim Lincecum (10-15, 5.15) is scheduled to start opposite San Diego's Edinson Volquez (11-11, 4.13). Lincecum is coming off a 7-2 loss to Arizona in which he tied his season high by allowing seven earned runs.