Yankees manager Aaron Boone revealed Friday that right-hander Tommy Kahnle has been shut down with right forearm tightness and will likely need to undergo Tommy John surgery. 

Before the Yankees' home opener, Kahnle had been placed on New York's 10-day injured list with a right ulnar collateral ligament injury, retroactive to July 28, as team officials initially believed the injury would not require surgery.

After an MRI and evaluation with team doctor Christopher Ahmad, however, the news got worse for the Yankees. Kahnle will be out for the season, and perhaps next.