SAN FRANCISCO -- This comeback win might have been the most shocking of all.

Little-used catcher Guillermo Quiroz came off the bench in the bottom of the 10th inning and crushed a solo homer to left to beat the Los Angeles Dodgers 10-9 at AT&T Park on Saturday night. The blast was the second walk-off homer in two nights for the Giants, who have come from behind in 11 of their 18 wins.

It was also just the third major league homer for Quiroz, a 31-year-old journeyman who was a surprise opening day addition to the roster as a third catcher.

"I don't think any of us expected him to hit a home run," manager Bruce Bochy said.

Quiroz didn't expect it, either. But thrust into one of the biggest spots of his career, Quiroz turned to a wealth of knowledge that he has been developing since beginning his career in Medicine Hat, Alberta, in 1999. Quiroz has played for five American League teams and caught Brandon League, now the Dodgers' closer, in Toronto and Seattle. With one out and an 0-2 count, Quiroz knew his former battery mate would turn to his splitter.

"I was just trying to hit something hard," Quiroz said. "I learned a while ago that you've got to take a shot and swing hard and see what happens."

The result was an improbable end to a wild night that nearly ended an inning earlier. In an odd twist, Quiroz's walk-off homer came an inning after reigning National League MVP Buster Posey hit into a double play with one out and the bases loaded.

"He said he was going to take me out to dinner because he was happy he didn't have to catch anymore," Quiroz said, smiling.

Posey might have to get in line. In his first season with the Giants, Quiroz already has earned the respect of the clubhouse veterans. Ryan Vogelsong's long journey back to the big leagues included a stint with Quiroz in the Venezuelan Winter League in 2004. Nearly a decade later, Quiroz clinched a win on a night when Vogelsong was charged with seven earned runs.

"I'm so happy for him," Vogelsong said. "I've known him for a while. It's great to see things happen for him."

As Quiroz was engulfed by the biggest media scrum of his career, Pablo Sandoval and Hunter Pence danced in the background.

"When good things happen to good people that do everything right, you couldn't be happier," Pence said. "It's an amazing moment. He's an awesome teammate who gets here early every day and does his work and is positive every day. He doesn't get many at-bats, but every time he gets up there he is prepared."

It's hard to imagine that Quiroz, who had just 12 big league plate appearances since 2010, could have been anticipating this moment. The Giants jumped out to a 5-0 lead and looked headed for a laugher. But Vogelsong gave up a barrage of hits in the fifth inning and was charged with seven earned runs in 42/3 innings.

"I just couldn't stop the bleeding there," Vogelsong said. "Its' a terrible feeling, but you've got to look at the positives."

Vogelsong gave up just one run through four innings and said he was throwing better. But by the end of his night, his ERA for the season was up to 7.20. Asked to sum up his night, Vogelsong shook his head.

"Crazy," he said. "Just like the whole game."

An Andres Torres solo blast started the latest comeback, and the Gants tied the game in the sixth. The rivals exchanged runs in the seventh, and both teams wasted good chances in the final innings.

Given a chance in the 10th, Quiroz didn't waste it. The homer was the first walk-off hit of his career and the Giants' first pinch-hit walk-off homer since Armando Rios' in 2000.

"We were just trying to end the game," said Bochy, who had only one more reliever available. "No, I wasn't expecting a home run off a tough closer like that. For him to do that is pretty impressive."

  • Center fielder Angel Pagan was pulled after a fifth-inning at-bat because of a right hamstring strain. Bochy said the strain is considered mild, but Pagan is unlikely to play Sunday night.

    Pagan, the Giants' leadoff hitter, is hitting .275 and leads the team with 24 runs.

    For more on the Giants, see Alex Pavlovic's Giants Extra blog at blogs.mercurynews.com/Giants