CHICAGO -- Cubs ace Kerry Wood will miss at least three weeks after tests Monday showed he has a muscle strain in his right shoulder.
Wood underwent an MRI exam that revealed the problem, the team said.
He will not be able to throw for three weeks and will then be re-evaluated by team doctors to devise a strengthening program.
"I feel bad for him. He's always been a guy who will go out there whenever possible and take his turn," general manager Jim Hendry said.
"It's unfortunate that it's going to put him out for a while. But at least it's a muscular problem that can heal and not a surgical problem. That's good news. It's not a tear. He will just have to take his time like with any muscle. And hopefully he can get back for the final two-thirds of the season," Hendry said.
Bothered by bursitis in his shoulder during spring training, Wood has had his last two outings cut short.
He left Saturday's game against the Astros after just three innings. In his previous start against Pittsburgh on April 24, he lasted only five innings. He is 1-1 in five starts with a 6.15 ERA.
"It feels good when I'm not throwing and it doesn't feel good when I'm throwing," Wood said.
He had been scheduled to pitch against the Brewers on Thursday.
Last season, Wood missed two months with an injury to his triceps muscle. He was sidelined all of 1999, one year after winning the NL rookie of the year award, following elbow ligament replacement surgery.
Glendon Rusch could move into Wood's spot in the rotation, as he did last season during Wood's stint on the disabled list.