SAN FRANCISCO -- Both starting pitchers had the Dodgers struggling for answers after their 7-2 loss to the Giants Sunday.

Chad Billingsley, Los Angeles' staff ace when he opened the season 5-0, is a slumping 0-4 with a 5.67 ERA in his last five starts after allowing three runs on eight hits in only four innings.

"I don't even know how to explain it," said Billingsley, 12-10 overall with a season-high 3.99 ERA. "It's frustrating."

Making the loss more frustrating -- it was former ace Brad Penny who beat them. An inspired Penny, pitching to keep San Francisco's flickering hopes for a National League Wild Card berth alive, lost a shutout on Russell Martin's two-run homer in the seventh inning, Martin's second home run in as many games.

Despite the loss, the Dodgers maintained their three-game lead over the Rockies, who fell in San Diego on Sunday, in the NL West.

"I guess a little bit," Penny said when asked if it was special beating the club that bought out the option year of his contract last winter.

With Manny Ramirez getting the game off to rest his legs, a rejuvenated Penny -- 3-0 with a 1.64 ERA since signing with the Giants after gaining his release from Boston -- left to a standing ovation after pitching seven innings, the Giants' newest former-Dodger Dodgers-killer.

"You never know what you'll get with him," said Andre Ethier, who had one of five hits off Penny. "He can go out there and feel good and have that stuff and be really confident, and sometimes he's not and he's laboring, like with players in general. You can see a different swagger and feel. He definitely had good stuff today."

Billingsley, not so much. He's allowed 38 hits over the last 27 innings and four homers in that span, including a two-run shot in the second inning by Juan Uribe that set the tone in this game. A fluky four-run sixth inning in Jeff Weaver's first game in a week provided a bulging 7-0 margin as the Dodgers missed a chance for a series sweep.

Manager Joe Torre, who lost Randy Wolf and Clayton Kershaw to freak injuries in the past week, isn't sure what to make of Billingsley's extended struggles.

"It looked like he was feeling for it," said Torre. "He didn't look like he was able to locate. He made a good pitch to Uribe, then tried to repeat and left it in the middle of the plate. It's sort of a domino effect. The psychological effect of not winning and trying to find a niche and a comfort zone, instead of trusting it and letting the ball come out of the hand.

"Physically is the one concern I had, and we talked in Arizona, and he assured me he was fine. I have to assume that's the case. It's in there somewhere. I know it's driving him nuts."

Billingsley gave that appearance as he struggled for the words to explain the way he's struggled on the mound.

"I don't think it's necessarily mechanical," he said. "I have to keep the ball down in the zone. I'm trying to figure something out and get this thing turned around. My cutter got hit today. It was spinning out of my hand and not moving much. That's what they were hitting."

Billingsley said making the proper correction is "easier said than done."

"It's not like I'm trying to throw every pitch belt-high," he said. "Maybe it's release point. You can look at video all you want, I know what I'm doing. Trying to correct it, sometimes it doesn't happen. I'm trying to get the rhythm back."

And Billingsley concedes it's in his head a little.

"When you're not playing well, yeah, it's getting to you," he said. "It's frustrating. I'm battling and going out there and hoping that today is the day to turn this thing around. When I'm out on the mound, I want to get after it. I'm not going out there with doubts.

"Physically, I'm fine. Mentally, I'm fine. It's frustrating. I'm feeling good out there. Some little things are throwing you off. It's frustrating."

With the Dodgers not hitting Penny, the game dictated Billingsley leaving for a pinch-hitter after four innings, trailing, 3-0. Jeff Weaver, appearing for the first time in a week, took over and pitched out of a jam for a scoreless fifth inning, but he allowed three cheap singles and a bases-loaded walk in the sixth. Ronald Belisario followed and allowed one run to score on a wild pitch and two more on Freddy Sanchez's single.