Collmenter will start Monday night against the Mets, which is the day Bronson Arroyo was slated to start.
Arroyo, who was behind the rest of the starters when the season began due to a back issue during Spring Training, will get an extra day of rest and start Tuesday night.
Delgado, who lasted just 3 1/3 innings in his start Thursday night, will try and get things figured out in the bullpen.
"You guys know we need innings out of guys, and he gives us a chance to win a ballgame," Gibson said of Collmenter. "He's shown that in 2011, he's done it out of the bullpen. Just looking at our options, we think that's the smartest way to go. We're going to go with this and see how it works."