Corpas (1-3, 5.88 ERA) missed four weeks with bone chips but returned after the All-Star break. He made two appearances -- a scoreless, one-hit game against the Padres on Saturday and an inning in which he gave up three runs to the D-backs in Monday night's 10-6 Rockies victory.
Although he wasn't sharp against the D-backs, he said he felt no problems during the game.
"After the game, I was in the house trying to eat something, and it was big [swollen]," Corpas said.
Ice and pain relievers didn't do the trick. Corpas was unavailable to pitch Tuesday and Wednesday, and opted for surgery. Dr. Thomas J. Noonan, the Rockies' medical director, will perform the procedure to clean out the loose bodies.
It will be the first surgery for Corpas.
The surgery complicates Colorado's uncertain bullpen picture.
On Tuesday, the Rockies demoted right-hander Joel Peralta, who had handled the eighth-inning role in Corpas' absence, to Triple-A Colorado Springs after a recent slump. Ryan Speier returned Tuesday after being on the disabled list since April with left hamstring and right shoulder issues, and manager Jim Tracy wants to make sure he's healthy and sharp enough to pitch in tight situations.
For now, Tracy is managing according to matchups, so key late-innings situations are going to right-handers Juan Rincon and Matt Daley, and left-hander Franklin Morales. The Rockies also will have to call up a reliever from Triple-A Colorado Springs before Friday's opener of a three-game series against the Giants.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.