AP Baseball Writer
SAN FRANCISCO (AP) -- Bruce Bochy had reigning NL MVP and batting champion Buster Posey as a perfect option off the bench to lead off the 13th inning.
Then, the San Francisco skipper blew it. Bochy's blunder put Posey in the wrong spot in the lineup without a chance to hit.
It wasn't the biggest mistake by the defending World Series champions, but it certainly helped cost the Giants in a 5-3 loss to the San Diego Padres on Monday night.
"I messed up the double switch. I got distracted," Bochy said. "I was out there arguing and I totally brain-cramped on that. Once I said it wrong, I was done. I knew that. That's a first. I probably should have stepped back and thought a little bit. ... Once I called it wrong I can't take it back. Got distracted, you're upset a little bit, that shouldn't happen but it did."
Will Venable made an incredible catch to save San Diego, and pinch-hitting pitcher Andrew Cashner drove in the go-ahead run with a perfectly executed safety squeeze in the 13th inning -- a night before his next start.
Venable's diving grab on the center-field warning track with his back to home plate ended the 12th and stole a game-winning hit from Juan Perez.
"When I hit it, I thought it had a chance to go over his head, because he was playing shallow," Perez said. "I put a good swing on it and the guy made an unbelievable catch."
Moments later, Alexi Amarista started the winning rally with a single and went to third on Chris Denorfia's single. Cashner came up to face Jose Mijares (0-1) and dropped a bunt single between the mound and third base for his sixth career hit and second RBI.
San Diego added another run on a bases-loaded walk from Jake Dunning on the way to its season-best seventh straight win. It was San Francisco's longest game of the year.
The Giants (35-34) couldn't hold a 3-1 lead for Barry Zito and dropped into fourth place in the NL West for the first time since April 8.
The Padres finally came through after they had two runners on and one out in the 11th and 12th, but Giants relievers Sandy Rosario and Javier Lopez got a pair of strikeouts to end each threat.
Joaquin Arias hit a sacrifice fly, Brandon Belt and Hector Sanchez each had an RBI single and Perez added two hits and a defensive gem on a night when the road-weary, injury-plagued Giants sent out a lineup largely of backups.
They landed in San Francisco about 3 a.m. Monday after a night game in Atlanta, showed up late to the ballpark and didn't take batting practice before the game. San Francisco just completed a grueling stretch with 14 of 18 games away from AT&T Park.
"We had a tough travel day," Bochy said. "They played hard, they played well. Had the lead. The bullpen did a great job 'til the end. This is baseball. You have to deal with tough losses."
Chase Headley hit a tying single in the seventh against Jean Machi, who induced an inning-ending double play by Jesus Guzman to avoid further damage.
Logan Forsythe had his first three-hit game this year for San Diego, swept in San Francisco's waterfront ballpark April 19-21.
Zito struck out a season-high eight and got back on track at home where he pitches so well, but had nothing to show for it as the Padres rallied against the bullpen. The lefty walked off to a standing ovation from the sellout crowd with two outs in the sixth and runners on first and third.
Machi relieved and threw a wild pitch that allowed a run to score, then retired pinch-hitter Nick Hundley on a groundout. Machi has allowed a run in six straight outings and 10 of his last 11.
Zito had his most strikeouts since getting 10 against Atlanta on Aug. 6, 2010.
Padres starter Edinson Volquez struck out six in five innings. He doubled leading off the third and scored on Denorfia's double for San Diego's first run.
Volquez knew Venable would make that clutch catch.
"I said, 'That ball, it's not going to bounce,'" the pitcher recalled saying. "He can run. He said he let down the team because he struck out."
San Francisco shortstop Brandon Crawford went 1 for 6 while batting third for the first time this season.
Bochy was asked before the game why he used Crawford there.