PITTSBURGH — Pittsburgh Pirates reliever Tyler Yates has undergone right elbow surgery and will miss the rest of the season.

Yates, out since mid-May, isn't expected to resume throwing for five to six months. The status of the Kaua'i native and former University of Hawai'i-Hilo pitcher for the start of next season is uncertain.

The right-handed Yates attempted to rehabilitate an injury that was initially described as elbow inflammation, but was shut down last week after showing little progress. He had surgery to repair the ulnar collateral ligament Tuesday in Birmingham, Ala.

Yates, 31, was 0-2 with a 7.50 ERA in 15 games before going on the 15-day disabled list on May 15. He had reconstructive surgery on the same elbow in 2002 and right shoulder surgery in 2005.