Brandon Belt was recalled from Triple-A Fresno to take Torres' spot on the roster.
Torres, who batted leadoff and played center field Friday, went 0-for-3 with three strikeouts in a 2-1 loss to the Marlins. On the season, the 33-year-old is batting .228 with three homers and 18 RBIs.
Giants manager Bruce Bochy said that Torres fouled a ball off his calf during the game and strained it.
"We're too shorthanded right now, so instead of waiting, we went ahead and made the move and brought Brandon to help us out," Bochy said. "[Brandon] gives us a left-handed bat. He'll help Aubrey [Huff] at first base and occasionally some outfield, too."
The 23-year-old Belt was hitting .309 with eight homers and 32 RBIs in 49 games with the Grizzlies. The Giants' top prospect has spent time at first base and the two corner outfield positions.
This marks the fourth time Belt, who was the Giants' Opening Day first baseman, has been with San Francisco this season. In 31 games, he has a .218 average with two homers and seven RBIs. Two of his 20 starts this year have come in left field.
"He's going to come up and help," Bochy said. "When you have a young player, you want to get him in there as much as you can, but at the same time, you have your veterans you still believe in. I will say I'll do all I can to get his at-bats in there, because I think we need some help, and now it's going to be up to Brandon to handle this well and get off some good at-bats."
Christina De Nicola is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.