Nationals pitching prospect Danny Rosenbaum had Tommy John surgery to repair a torn ulnar collateral ligament on Thursday, a source told CSNwashington.com.
Rosenbaum, 26, will now begin a 12 to 18 month recovery process to return from the procedure. The lefty starter made four appearances this season with the Triple-A Syracuse Chiefs before suffering the injury.
Rosenbaum went 1-1 with a 4.50 ERA in those games with the Chiefs. The former 22nd round pick also appeared with the Nationals in major league spring training, going 0-1 with a 2.70 ERA in three outings.
The Nationals drafted Rosenbaum out of Xavier University in 2009. In six minor league seasons he holds a 3.12 ERA across 121 total games.