"[The MRI results] came back clean, which was really good news," Molitor said. "It's been determined there is a little inflammation in that elbow, so we're going to have to back him off a little bit to make sure he gets back to 100 percent."
The Twins are optimistic Nolasco will be on the disabled list for just the 15 days, Molitor said. Nolasco felt discomfort on a pitch to the Tigers' Alex Avila in the fourth inning on Wednesday, but he remained in the game to face two additional batters. Nolasco allowed six runs, six hits and four walks in three-plus innings. He informed the training staff about his elbow after exiting the game.
May, who is ranked as the Twins' 11th-best prospect, according to MLB.com, had been scheduled to pitch Saturday for Triple-A Rochester. He threw a side session on Thursday.
"Given the way the off-days are falling and where we are in the rotation, it's going to be his turn to pitch," Molitor said. "It'll be a great opportunity on Opening Day at home."
"He was one of the last cuts," general manager Terry Ryan said about May. "He had a nice spring for us. He was in the mix for us right to the end. Of course, he's fresh, so he'll be able to go."
Ryan said the Twins put little thought into pushing Phil Hughes back from his Sunday start to pitch Monday's home opener. Ryan said it's crucial to keep pitchers on their scheduled days.
The Twins will be down two starting pitchers with the injury to Nolasco and Ervin Santana's suspension.
"It didn't take us long," Ryan said. "I warned people that we did send down. There was some disappointment in that room that particular day. I just said, 'Be ready. Things happen.' I didn't think it'd happen so quick. I certainly didn't have much interest in having it happen so quick. But it has."
May went 3-6 with a 7.88 ERA in 10 appearances, including nine starts, with the Twins last season. He is 54-46 with a 3.90 ERA over seven Minor League seasons.
"You know a kid is going to be emotional getting a chance to perform on that stage on Opening Day at home, but emotion can be an asset, if you know how to use it," Molitor said. "Last year, we did see a little of that emotion maybe not used properly, maybe worked against him at times, but that's what experience is about, and he brought kind of a new approach to Spring Training in addition to pitching well."
In other injury news, Molitor said that backup catcher Chris Herrmann is doing well after getting hit in the mask with a foul tip on Thursday. Herrmann exited after two innings with a cut above his nose, but he might play again on Saturday.