Torres was placed on the 15-day DL on Friday, a day after he injured his hamstring rounding first base running out his fly ball in the second inning of a 7-2 victory over the Philadelphia Phillies.
He was on the disabled list with the same injury from April 28-May 25, missing 26 games. Torres had an MRI on Friday and said he doesn't think it's as serious this time, hoping he will come off the disabled list when he's eligible.
With Torres out and Nate Schierholtz also on the disabled list with a strained left hip, the Giants are short-handed in the outfield.
"We were trying to avoid it," manager Bruce Bochy said of Torres going on the DL. "We were hoping to get good news. He's very valuable to this ballclub. That's a tough loss for us."
The switch-hitting Torres is batting .247 with two home runs and 13 RBIs in 53 games and 11 of his 22 hits have gone for extra bases. He has five stolen bases.
"It's amazing" it's happened a second time, Torres said. "But it's not as bad."
The Giants called up infielder-outfielder John Bowker from Triple-A Fresno and plan to use him off the bench.
It could be a short stay for Bowker considering the club plans to make a move Saturday to clear roster room for newly acquired second baseman Freddy Sanchez.
Sanchez came to the Giants in a trade with Pittsburgh on Wednesday but is nursing an inflamed left knee. Bochy said he could be available as a pinch-hitter Saturday and perhaps make his debut in the lineup Sunday in the series finale against the reigning World Series champions.
"He will do some stuff tomorrow, groundballs and take batting practice," Bochy said. "We'll evaluate him and he'll possibly play on Sunday."
Sanchez will join the team Saturday, but his locker is ready and waiting for him in the clubhouse. Bochy didn't rule out Sanchez pinch-hitting Saturday. He spent the past couple of days getting settled into a place to live.