An MRI performed Monday revealed no further damage and Sheets is expected to have additional tests Tuesday. According to ESPN The Magazine's Buster Olney, a source close to Sheets said he is expected to be out two weeks and not several months like Detroit Tigers pitcher Joel Zumaya, who has been out since early May with a similar injury.
Sheets was injured during his start Saturday against the Rockies in the fourth inning. He threw a pitch to Colorado's Todd Helton and immediately grimaced in pain. Sheets left and was replaced by rookie Yovani Gallardo, who is a candidate to replace him in the rotation.
"When I couldn't put pressure on the ball [Saturday night], that's when I stepped off the rubber," Sheets said after the game.
Sheets is 10-4 with a 3.39 ERA for the Brewers, who lead the NL Central by 3½ games over the Cubs.
Sheets has dealt with pain this season but did not miss any starts. He was forced from a game after three innings on April 25 at Wrigley Field when he suffered a slight groin strain. And in May 22 in Los Angeles, he developed a blister on his middle finger and left the game in the seventh inning.
Rookie Yovani Gallardo (1-1) is scheduled to take Sheets' spot
in the rotation Thursday when the Brewers host Arizona.
Meanwhile, the Brewers also placed reliever Chris Spurling on the bereavement list so he can tend to a family emergency. Spurling is expected to return Thursday or Friday.
Milwaukee called up lefty starter Manny Parra and reliever Grant Balfour from Class AAA Nashville to fill out the roster.
In four starts, Parra was 3-1 with a 1.73 ERA, including a perfect game. Parra is expected to join the bullpen and provide middle relief.
The Brewers claimed reliever Balfour off waivers from Cincinnati
over the winter after he had shoulder and elbow surgeries. In 23
relief appearances with Nashville, he was 1-1 with a 1.74 ERA and
six saves, with 46 strikeouts in 31 innings.
Information from The Associated Press contributed to this story.