The Giants had faced the possibility of skipping Cain's turn in the rotation to use their top three starters against the Dodgers. Such a move involving Cain, who's struggling yet widely respected, would have created anxiety.
However, shelving Cain will enable the Giants to avoid fuss as they assign Madison Bumgarner, Johnny Cueto and Matt Moore to face the first-place Dodgers, in that order, Tuesday through Thursday. Monday's scheduled off-day will enable the trio to receive their usual four days' rest.
The Giants won't need a fifth starter until Aug. 27, the middle game of a three-game series against Atlanta. Right-hander Jake Peavy, who was sent to the bullpen after the Giants acquired Moore at the Trade Deadline, likely will receive that start.
This marked the third trip to the DL this season for Cain, who's 4-8 with a 5.81 ERA in 17 starts. Right hamstring injuries accounted for his previous two stints. Giants manager Bruce Bochy said that the 31-year-old reported back discomfort after his five-inning, six-run performance Wednesday against Pittsburgh.
"It was grabbing him pretty good," Bochy said.
Right-hander Cory Gearrin was reinstated from the DL to fill Cain's vacancy on the active roster. Gearrin, 3-1 with a 3.89 ERA in 41 relief outings, hadn't appeared in a game for the Giants since July 5 due to a strained throwing shoulder.
Chris Haft has covered the Giants since 2005, and for MLB.com since 2007. Follow him on Twitter at @sfgiantsbeat and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.