Johnston (undisclosed) was injured in the first period of Saturday's game versus the Flyers, Arthur Staple of The Athletic reports.
Johnston fought Samuel Morin early in the game, and the former left for the locker room. The 27-year-old Johnston didn't return after either the first or second intermissions. It's unclear what he hurt in the fight. If he doesn't get back on the ice Saturday, his next chance to return is Tuesday versus the Capitals.