Before Sunday's home opener, Cordero felt a sharp pain in his shoulder during batting practice and immediately told the training staff.
"I'm not going to really know until I start throwing on Wednesday," Cordero said. "Hopefully everything will be all right and the shot will knock it out."
Cordero said he has had some shoulder tightness during Spring Training, but felt it had nothing to do with his recent injury. Even the miles per hour on Cordero's fastball was down, but he said he was working things on the mound.
"At that point, I wasn't throwing hard at all," he said. "I was just working on a bunch of stuff."
Cordero said it was weird that he couldn't pitch the ninth inning against the Braves on Sunday. Instead, Jon Rauch came into the game and won his first game of the season.
"I wanted to go out there and get the first save at the new stadium," Cordero said. "That would have been awesome. It would have been a cool experience. Unfortunately, I wasn't able to do it."
In the meantime, manager Manny Acta said the rest of the bullpen will step up in their roles, with Rauch as the closer. The skipper indicated that right-hander Joel Hanrahan could pitch some meaningful innings. Entering the season, he was looked upon as a long reliever.
Bill Ladson is a reporter for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.