St. Louis placed its ace on the 15-day disabled list on Friday due to a muscle strain in the back of his right shoulder -- the teres major muscle, to be exact. The move was made retroactive to Monday. Carpenter already had been scratched from his scheduled Friday start as a result of the injury.
"I think it's a logical move," general manager John Mozeliak said on Friday. "It's precautionary."
The DL move means Carpenter will have to miss at least one more turn, and he will be eligible to return to the active roster on Aug. 26 -- the first day of a two-game set between the Cardinals and Brewers at Busch Stadium. St. Louis pitching coach Dave Duncan said the hope is that Carpenter will pitch in the series after that, Aug. 29-31 against the Astros at Minute Maid Park.
In the interim, the Cards have four off-days in the next two weeks, allowing them to use a four-man rotation if they so desire.
"The way we [are] set up with the off-days, talking to [manager Tony La Russa] and [Duncan] last night, it seemed to make a lot of sense," Mozeliak said. "More importantly, we don't want to put Carp in a position where we don't need him to be if we can buy a few extra days."
The teres major is a muscle very close to the triceps, where the club originally believed Carpenter's injury was located.
Carpenter made three starts after returning from Tommy John elbow reconstructive surgery. He pitched four effective innings in his first game, five scoreless frames in his second and he went 5 1/3 in the third before experiencing pain in his arm and leaving the game Sunday night against the Cubs.
Carpenter will not pick up a ball until Tuesday, when he hopes to begin a throwing program by playing catch.
"He's not going to be able to do something serious about throwing until Tuesday, and there's no way you're going to put him in a game before a week from then," La Russa said. "At the soonest, that's two weeks. So there's no reason not to use that spot for something to help the club."
Outfielder Brian Barton will take Carpenter's spot on the active roster. Barton had been sidelined since July 6 with a fracture in his right wrist. He completed a 20-day Minor League rehabilitation assignment at Triple-A Memphis on Monday.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.