In a corresponding roster move, the Pirates recalled infielder Brent Morel from Triple A Indianapolis.
"Charlie started feeling a level of discomfort a couple of months ago," Pirates manager Clint Hurdle said to MLB.com. "It's been manageable lately, but now it has started to affect his performance -- and that's when you have to take a closer look at it."
Morton is 5-12 with a 3.84 ERA and 120 strikeouts in 25 starts this season. He hasn't won since July 19.
- Scooby Axson