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07/31/12 8:36 PM ET

Feliz to undergo Tommy John surgery

Right-hander to miss much of 2013 season while rehabbing elbow

ARLINGTON -- Rangers pitcher Neftali Feliz has been diagnosed with a torn ulnar collateral ligament and will undergo Tommy John elbow reconstruction surgery on Wednesday. He will miss the rest of the season and much of 2013.

It's a major blow for the 24-year-old right-hander, who served as closer for the Rangers the past two seasons -- making the All-Star team in 2010 -- before moving into the rotation this year. The surgery will be performed Wednesday by Dr. Keith Meister, and the normal recovery time is about 12 months.

Feliz could be back pitching for the Rangers at the end of next season, but he probably won't be back to full strength until 2014. He is eligible for free agency after the '15 season.

"It's a challenge for him," general manager Jon Daniels said. "We all felt he was making major strides as a starter before he started having issues. It will be a challenge for him to push through this. Fortunately, the nature of the injury, guys do come back from it. The success rate for the surgery is high. He'll get through this and come back. It's an opportunity for him to improve in other areas, but it's going to be a challenge for him."

Feliz was 3-1 with a 3.16 ERA in seven starts and one relief appearance for the Rangers this season. His last start was against the Astros on May 18, when he allowed one run in 4 2/3 innings in the Rangers' 4-1 victory.

Feliz reported soreness after that start, and he was subsequently placed on the disabled list with a sprained right elbow. He made three starts on a medical rehabilitation assignment earlier this month, going 0-2 with a 1.36 ERA, but he was scratched from his latest start for Triple-A Round Rock on Sunday due to more elbow pain.

The Rangers knew that Feliz had a serious injury, but they declined to reveal it until after the Trade Deadline.

"It wasn't until two days after his last rehab start that he came in and told our guys he was feeling a little bit sore," Daniels said. "From that, we did all the diagnostics and testing and had an MRI, and that confirmed that he needed surgery."

Feliz is the second member of the Texas rotation to require season-ending surgery. The Rangers also lost pitcher Colby Lewis earlier this month with a torn flexor tendon. He also underwent surgery and will be sidelined 9-12 months.

The Rangers were able to reinforce their rotation by acquiring veteran right-hander Ryan Dempster from the Cubs for Minor League infielder Christian Villaneuva and pitcher Kyle Hendricks.

T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.