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SAN DIEGO (Reuters) - Pitcher Aaron Harang foiled San Francisco's plans of maintaining momentum in the chase for a playoff berth by leading the San Diego Padres to a 3-1 victory over the Giants on Wednesday.

The defending World Series champions had hoped to sweep the three-game series against the Padres and close the gap at the top of the National League West, but Harang (13-5) shut down San Francisco (75-68) by allowing just one run in seven innings.

San Diego's Jesus Guzman chipped in with an RBI single in the sixth inning to break a 1-1 tie, before Cameron Maybin's RBI triple in the eighth completed the scoring.

Padres closer Heath Bell pitched the final 1 1/3 innings to record his 36th save of the season.

The win was just the second in 13 games for the NL West cellar-dwelling Padres (62-81) and it dropped the Giants seven games behind division-leading Arizona.

Trying to keep San Francisco's playoff hopes from slipping further, starter Matt Cain (11-10) tossed seven innings and allowed just two runs but still had to settle for the loss.

"But he keeps grinding out there for you."

Cain allowed a solo blast to Will Venable in the first to fall behind 1-0, but the scores were tied in the fifth when San Francisco rookie Brett Pill homered for a second straight game after going deep in his first career at-bat on Tuesday.

Pill was also thrown out at home plate in the seventh while trying to score the potential game-tying run, with Venable making the throw from right field.

"It was nice to make a play for (Harang). Because the last time I was out there with Aaron pitching, it didn't go so well," said Venable, who made a poor defensive play during Harang's previous start, a 3-0 loss to Colorado.

"This was a good team win."

(Editing by John O'Brien)