CINCINNATI -- Right-hander Alex Cobb was placed on the 15-day disabled list Sunday with a left oblique strain.

Cobb returned to the Tampa Bay area on Sunday for an MRI that revealed the injury.

"I wouldn't say shocked, because I did feel something during the game that was pulling a little bit," Cobb said during a conference call when asked about his reaction. "Very disappointed in the fact that it's typically a lengthy rehab process because you can't do too much to speed up the healing process. You have to let it really heal up on its own. That was really disappointing to hear that."

The timetable for Cobb's return is unknown at this point, but normally injuries like his take from four to six weeks.

"That's what I keep being told," Cobb said. "That's been the hardest part for me to really grasp and understand, because it doesn't feel like that lengthy of an injury. I feel healthy walking around the house, doing daily activities, it's not that bad.

"...[But] I get the MRI and hear the professionals telling me it's going to be four to six weeks, it's still hard for me to believe that. ... That's probably going to be the reality of it."

The Rays recalled left-hander Jeff Beliveau from Triple-A to take Cobb's roster spot on Sunday. Beliveau was then optioned back to Durham after notching a scoreless fourth in Sunday's 12-4 loss to the Reds. The Rays will make another move on Monday to bring in another reliever.

Veteran left-hander Erik Bedard, who was selected from Durham on Saturday and pitched two innings of relief on Sunday, will take Cobb's spot in the rotation and start against the Yankees on Thursday.

Cobb earned his first win of the season Saturday, when he pitched seven scoreless innings in the Rays' 1-0 win over the Reds. Cobb left that game after just 87 pitches when Rays manager Joe Maddon elected to use pinch-hitter Logan Forsythe in the top of the eighth, a decision that Maddon now says was motivated by the condition of Cobb's oblique rather than the situation of the game.

"Stuff-wise, it was among the best you're ever going to see him throw," said Maddon in describing how he felt perplexed by the situation during Saturday's game. "So that was really confusing. So he came off and I was hoping [head athletic trainer] Ronnie [Porterfield] would tell me that it was dehydration. But upon examination, he was just a little concerned that there might be an oblique strain in there."

Cobb said he felt the injury after using a changeup to strike out the first batter of the game, Billy Hamilton.

"He swung over it for strike three and I just felt something grab right there," Cobb said. "Then basically throughout the game I was feeling it. I was hoping it was just a cramp or a slight pull maybe that would heal in a few days ... two or three at the most."

Cobb noted that he suffered the exact same injury in 2010 at the end of Spring Training prior to starting the season with Double-A Montgomery. He did not make his first start for the Biscuits until May 5 of that season.

Of the five pitchers projected for the Rays' starting rotation for the 2014 season, three are now on the disabled list. In addition to Cobb, Matt Moore went on the 15-day disabled list Tuesday and is waiting to learn more about the condition of his left elbow, and Jeremy Hellickson, who had "loose bodies" removed from his right elbow in January, was placed on the DL just before the season began. Hellickson is expected back in June.

In addition, the Rays' depth took a hit when right-hander Alex Colome tested positive for PEDs during Spring Training and was suspended for 50 games.

Maddon referred to not having Moore and Cobb at this point of the season as "kind of an awkward thought."

Ironically, all three of the pitchers who competed for the fifth spot in the rotation during Spring Training -- Jake Odorizzi, Cesar Ramos, and Bedard -- are now in the rotation.

"Speaks to the word depth," Maddon said. "We really try to honor that thought. We're very serious about how we set this whole thing up. We still have other candidates in Triple-A that you like, too, if anything else were to happen. But it's all about depth. Because nobody's going to feel sorry for you and I don't want us to feel sorry for ourselves, either."