Pitcher Jose Alvarado has been activated from the paternity list in a corresponding move.
The Rays removed Morton from his start against the New York Yankees on Sunday after just two innings, but he didn't seem concerned about the injury.
"I think the fortunate thing was that it really didn't progress past anything that was intolerable," he told reporters after the game. "It was just kind of some discomfort back there and tightness."
"I really think it's just going to be just managing the symptoms and how it feels going forward. It's just the kind of thing where I don't really know where that's going to lead here in the next three, four, five days. It's just going to be the kind of thing where I'm just going to have to be honest with my symptoms. ...
"The hope being it just doesn't become anything that's an issue here in the coming weeks and months. But I don't foresee that at all. I've had issues, and I'm pretty confident this is very manageable."
Morton, 36, is 1-1 on the season in four starts with a 5.40 ERA, 1.50 WHIP and 17 strikeouts in 16.2 innings. He served as the team's Opening Day starter this season.
"We knew something didn't feel right and didn't think it was smart to just continue to try and push through it," manager Kevin Cash told reporters after Sunday's game. "We need Charlie Morton to be really good for us the rest of the way, and if we have to shave off a start right there today, then I think we made the right decision."