CINCINNATI -- The Reds placed starting pitcher Edinson Volquez on the 15-day disabled list on Thursday because of back spasms and recalled pitcher Homer Bailey from Triple-A Louisville.

Bailey will take Volquez's rotation spot and start on Saturday against the Indians at Great American Ball Park.

Volquez underwent an MRI exam Thursday morning, one day after persistent back soreness stopped his side bullpen session after a couple of pitches.

"It's muscular. Nothing in his vertebrae or anything like that," Reds manager Dusty Baker said. "That's positive news. We just decided that instead of sending him out there 75-80 percent, we'll get him well and skip one start and get him back to 100 percent."

Volquez's DL stint is retroactive to Sunday. In the sixth inning of Saturday's 6-5 loss to the Padres in 16 innings, the 25-year-old left after mid-back spasms started to bother him. Volquez was originally slated to start on Friday, but was switched with Saturday starter Bronson Arroyo with hopes the extra day of rest would help.

It was Volquez who went to Baker and suggested he not pitch and asked for the MRI. This season in eight starts, the right-hander is 4-2 with a 4.25 ERA. Last season, Volquez was a 17-game winner and Cincinnati's lone All-Star.

It became a necessity to promote Bailey once Ramon Ramirez was used for 2 1/3 innings of relief during Thursday's 12-5 loss to the Phillies. Ramirez was a starter at Louisville until his recall Tuesday to replace the injured Nick Masset in the bullpen.

In eight starts this season for Louisville, the 23-year-old Bailey is 3-5 with a 4.57 ERA, 17 walks and 43 strikeouts over 45 1/3 innings. Once heralded as the organization's best young starter, Bailey has gone 4-8 with a 6.72 ERA in 17 Major League starts since 2007.

A strong contender for the fifth spot of the Reds' rotation, Bailey posted a 2.61 ERA in six Spring Training games, but ultimately lost out to Micah Owings.

Bailey has had some mixed results in the Minors this season. His best outing was seven scoreless innings on May 5. In his last start Monday against Norfolk, a loss, Bailey gave up two earned runs and six hits over six innings while throwing 90 pitches.

"Hopefully he can come up here and do the same thing," Baker said. "We need it. He needs it and wants it."