"Unfortunately our best pitcher, if not the best pitcher in baseball right now, comes up a little lame with his lat," Cubs manager Dale Sveum said. "There's no timetable. We're going to make sure that thing is back and ready to go 100 percent by the time he gets back."
The Cubs have decided to take a conservative approach with Dempster (3-3, 2.11 ERA). Randy Wells (1-1, 4.50 ERA) will sub for the right-hander on Wednesday in the series finale against the White Sox, making his third start of the season.
"It's gotten harder and harder to get loose and maintain," Dempster said. "I felt I was going south the way I was feeling instead of feeling better each time. I'm going to try to give it some rest and get it back and ready to go back out there."
"We're going to play it conservatively with this one as well as he's throwing," Cubs president Theo Epstein said. "We want to nip this in the bud so it doesn't turn into a strain or anything like that."
The subject of trade rumors, Dempster has won his last three starts after going 18 starts without a win. In those games, he's gave up 11 hits and walked three over 22 scoreless innings, which has definitely enhanced his value to a playoff-bound team.
"I should've pitched through it then," Dempster quipped when asked if this might hurt his marketability. "I'm not worried about that. I'm more worried about trying to get healthy."
Said Epstein: "Generally, when players have these minor injuries, it's typical to wait until they come back and re-establish their health before engaging any serious trade talk."
This is Dempster's second turn on the disabled list this season after missing time in April with a right quad strain.
"I'm a pretty good judge of my body, so when it tells me I'm ready to go, I'll go again," said Dempster, who felt some discomfort in his start June 5 against the Brewers.
As for his scoreless-inning streak, Dempster joked that he's aiming for Orel Hershiser's record 59-inning streak.
"I wanted to sit on that for a little while -- make Orel Hershiser sweat it," he said.
Left-hander Scott Maine was recalled from Triple-A Iowa to take Dempster's spot on the roster.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter@CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.