Manager Craig Counsell said Peralta's replacement in the rotation will be announced on Thursday.
"It's something that it's kind of time for, we think," Counsell told reporters. "It's a big change for him, and it's not easy to make that transition during the season. But we'll get him in there and I think he has a chance to be real good at it."
Peralta is 4-2 in eight starts, but he has a 6.08 ERA in 40 innings pitched.
Peralta has made 120 career starts. He has thrown only one inning of relief -- his major league debut in April 2012.