The assault happened at a bar on the 100 block of Chesnut Street on Oct. 7, PPD said. The attacker walked up behind the victim and punched him several times, knocking him to the ground, investigators said.
The victim, 25, needed 17 stitches for a deep gash to his calf, police noted.
The suspect is described as a bearded man wearing a number 26 Chase Utley Philadelphia Phillies jersey with dark pants and two-tone Nike sneakers.
Anyone with information should call PPD's tipline at 215-686-8477 or submit a tip anonymously online.
Click here to follow Daily Voice Bethlehem and receive free news updates.