McClellan exited his appearance against the Giants on Thursday because of elbow discomfort, and he told reporters after the game that he had been feeling soreness in his right elbow for a couple of weeks. McClellan had a pair of surgeries on that elbow when he was in the Minors.
McClellan, who underwent an MRI exam in St. Louis on Friday, will be shut down for the next six weeks. If he is able to fully heal during that time, he'll then begin a throwing program. If the period of rest does not take care of the issue, surgery would be reconsidered.
The Cardinals called up right-hander Brandon Dickson from Triple-A Memphis to take McClellan's spot in the bullpen; however, the loss of the veteran reliever takes away another one of manager Mike Matheny's strongest options against left-handed batters.
When the club released J.C. Romero earlier in the week, it was expected that McClellan would be able to help mitigate the effects of having only one lefty remaining in the bullpen. Now that burden will fall largely on Victor Marte.
Allen Craig, who, like McClellan, has been placed on the disabled list, was also examined back in St. Louis on Friday. He has been diagnosed with a mild hamstring strain, suffered while trying to make a diving catch on Wednesday. The injury is not considered serious, but the Cardinals needed to be proactive in calling up another outfielder since Carlos Beltran (knee soreness) has also been recently limited.
"Given the uncertainty with other players, we couldn't continue to piece together a lineup," general manager John Mozeliak said.
Craig's DL stint is retroactive to May 17, and the Cardinals are optimistic that he'll be ready to return when the 15-day period is up. He will remain in St. Louis while the team wraps up this road trip.
Taking Craig's spot on the roster is outfielder Adron Chambers. Both Chambers and Dickson are available for Friday's game.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.