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SAN FRANCISCO -- Matt Cain endured several years of little run support with no complaints. So, imagine his joy at watching Nate Schierholtz's inside-the-park home run highlight San Francisco's latest win.

"I don't think I could run that fast even if there was no fence," Cain said.

He pitched a four-hitter for his seventh straight victory and the Giants beat the Oakland Athletics 7-1 on Sunday for a three-game sweep.

Pablo Sandoval added a two-run homer and Andres Torres matched his career high with three hits, including a triple, as the Giants won for the ninth time in 12 games and earned their second three-game sweep of the season. They hadn't swept the A's at home since June 15-17, 2001.

Cain (9-1) ended a four-start losing streak against the A's. He retired 15 straight after Jack Cust's third-inning double before pinch-hitter Nomar Garciaparra reached on an error in the eighth.

Cain hasn't lost since his second outing of the year back on April 15 and sure is making a case for his first All-Star nod. He struck out a season-high nine and walked none in his third complete game of the season and second in three starts. He struck out Jason Giambi with his 119th pitch to end the 2-hour, 9-minute game.

"That's an opportunity you want to take advantage of," Cain said of finishing. "These guys are giving me tons of [run] support. Everything's clicking right now."

Schierholtz lined a pitch from Brett Anderson (3-7) to triples' alley with two outs in the third inning and took off. He easily beat the throw to the plate.

It wasn't until Schierholtz saw third-base coach Tim Flannery -- jumping up and down in his typical emphatic fashion -- signaling him home that he realized he had it. Flannery has seen five of them from his coaching position: Ruben Rivera, Bret Boone, Steve Finley, Tony Gwynn and now Schierholtz.

"I wasn't stopping him. I went up the line and greeted him. I was the greeter," Flannery said. "This looked like we had it all the way. It's nice to be a part of it and get a little Adrenalin hit at 51 years old."

The inside-the-park homer was the fourth at 10-year-old AT&T Park, and the third in regular-season play. Seattle Mariners star Ichiro Suzuki did it during the 2007 All-Star game. Dustan Mohr is the only other Giant to hit one, on Aug. 4, 2004. Fernando Vina was the first to do it in the Giants' waterfront ballpark on May 9, 2000, while with the Cardinals.

Cust also homered for the A's, who lost their third straight and fifth in six. They were swept in a three-game series for the fourth time this season.

Oakland lost to reigning NL Cy Young Award winner Tim Lincecum on Friday night, then recent 300-game winner Randy Johnson on Saturday.

"We ran into a guy who won the Cy Young last year and a guy who would win it this year and a guy that's won five or six of them," Cust said. "When I saw that we drew those guys a couple weeks ago, it's not something that you're licking your chops about."

Schierholtz, the right fielder, also showed off his arm when he threw out Jack Hannahan at second trying to stretch a second-inning single into a double. He's been playing so well that manager Bruce Bochy is intent on increasing his playing time.

Cain had lost four straight to Oakland dating to his only win in the series on May 21, 2006, during his standout rookie season. He also hit his fifth career double in the second off Anderson, who has lost three of his last four starts.

Cain fell behind in a hurry after Cust's one-out homer in the first, only to see Randy Winn tie it on a sacrifice fly in the bottom half just before Sandoval's sixth homer of the year. Edgar Renteria also added a sacrifice fly for San Francisco.

Game notes

Cain threw 87 strikes. ... Giambi returned to the Oakland lineup after being scratched Saturday night with tightness in his right calf. ... The A's fell to 1-5 in interleague play. ... Soccer star Mia Hamm, married to Garciaparra, played in the annual wives' softball game to benefit local children's hospitals. The SS went 2 for 4 with a two-run homer but the Giants wives rallied for a 16-15 victory. ... The Big Unit shared bottles of champagne marked with "300" with his teammates and coaches Saturday night.