GOODYEAR, Ariz. — Kerry Wood went one full season in Cleveland without making a trip to the disabled list. He won't make it two.

The Indians' closer, with a long history of injuries and surgeries, could miss two months with a strained muscle in his upper back, an injury that was not initially believed to be serious. Trainer Lonnie Soloff said Saturday that an MRI exam on Wood revealed a "moderate" strain. He said Wood will be out a minimum of six weeks.

While Wood is sidelined, right-hander Chris Perez will take over as Cleveland's closer.

"I think Chris can handle the job," Indians general manager Mark Shapiro said. "It's on an interim basis. The situation with Kerry is not one we think is going to be long term. It's disappointing, but you don't usually go through a spring without some challenging news.

"This is the first challenging news we've had. We'll face it and get through it," he said.

Wood felt soreness after throwing one inning in an exhibition game on March 10. He was scratched from his next scheduled appearance three days later, and the Indians continued to insist that there was nothing to worry about with the 32-year-old righty.

But when the soreness lingered, the team decided to have Wood undergo further tests. He has been placed on the DL 12 times in his career. He's about to make it 13.

Soloff said Wood, who had 20 saves in 26 chances last season, did not injure himself on one pitch, but rather it was "an attritional thing over time." Soloff said Wood has had soreness in the muscle during spring training for the past four or five years.

Wood will begin conditioning work next week and start playing catch in 10 to 14 days.

"If there is one positive, it's not his elbow or shoulder, where he has experienced surgical issues in the past," Soloff said of Wood, who had an elbow operation in 1999 and one on his shoulder in 2006.

Wood has been relatively healthy the past few years. His last trip to the DL was for a blister on his finger in his final season with the Chicago Cubs.

The Indians signed Wood to a two-year, $20.5 million contract before last season. At the time, it addressed a glaring weakness for a team still considered among the AL's upper class. But Cleveland traded Cy Young winner Cliff Lee and All-Star catcher Victor Martinez last season, signaling the start of another rebuilding project.

There had been speculation the Indians might try to deal Wood and his salary this season if they drop from contention. Any such plans are now on hold.

Perez, who came over in a trade from St. Louis last season, was not aware of Wood's injury.

"It stinks for our team because we were hoping he would bounce back big this year," Perez said. "At the same time, other people have to step up, and I guess that starts with me. I'll try to not miss a beat and keep doing what I've been doing."

Perez had one save last season with Cleveland, which acquired him in exchange for third baseman Mark DeRosa. The 24-year-old's long-term goal is to close. He's getting an early audition to show if he can.

"It's a great opportunity. I'm excited," he said. "Obviously, I hate to get it at the price of a friend and teammate, but he'll be back. I'm working my way toward being a closer some day for somebody. Hopefully, I go in there and do my job and Kerry comes back and gets slid back into the closer's role and I get bumped into the eighth-inning role and it just makes our bullpen better.

"It might help us out in the long run."