Rangers coach Alain Vigneault made the surprising announcement Friday on the first of two off days in the series New York leads 2-1. Prust wasn't penalized in the first period of Montreal's 3-2 overtime win Thursday night, but he faces an NHL hearing Friday and a possible suspension.
Stepan had X-rays Thursday night that were negative, and he returned to the game. He was in pain after the game and on Friday morning.
Further tests after a visit to a specialist revealed the fracture. Vigneault says his playing status for the rest of the series will be determined after surgery.