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."
Feliz, 24, was scratched from his planned Triple-A rehab start last weekend with discomfort in the elbow and once he was examined, the tear was revealed. He had been on the disabled list since mid-May.
Feliz made the move from closer to the rotation before the 2012 season.
He was the 2010 AL Rookie of the Year as the club's closer with 40 saves and collected 32 more saves last year. But with the signing of Joe Nathan in the offseason, the Rangers had the luxury of moving Feliz to the rotation.
He was 3-1 with a 3.16 ERA in eight games (seven starts) in 2012 with 37 strikeouts and 23 walks.