Robert Gsellman has at least some degree of labrum tear in his non-pitching shoulder, reports Adam Rubin of ESPN New York.
Team doctors will wait until after the season to determine whether Gsellman will require surgery.
Gsellman has not been swinging the bat at all in Las Vegas or with the Mets, which has made the issue glaring, adds Rubin.
After tossing 5,2 scoreless innings in a non-decision against the Nationals on Wednesday, Gsellman has a 3.08 ERA over five appearances including four starts since being called up.
