ARLINGTON, Texas -- Texas Rangers pitcher Neftali Feliz is out for the season after tearing his ulnar collateral ligament in his pitching arm.

He'll have Tommy John surgery Wednesday, performed by Rangers team physician Dr. Keith Meister.

Manager Ron Washington also announced that Roy Oswalt, who allowed eight runs on 11 hits in Monday's 15-8 loss to the Los Angeles Angels and has struggled to find consistency in his six starts in Texas, will be moved to the bullpen. Ryan Dempster, acquired minutes before Tuesday's non-waiver trade deadline, will take his place. Dempster's first start is slated for Thursday.

General manager Jon Daniels admitted that the club knew about Feliz's status for a few days but didn't want to say anything until after the deadline.

"It's a blow for him and for the club," Daniels said. "Doctors feel he should be a perfect candidate to have a 100 percent recovery and be back at some point next summer assuming all goes well."