With the puck nowhere near Drysdale, Johnston caught him with a big open-ice hit in the Ducks defensive zone. Drysdale stayed down on the ice before eventually making his way to the Philadelphia locker room.
Johnston was assessed a five-minute major and a game misconduct for interference after a review.
Drysdale, 23, has been an important part of the Flyers’ blueline this season. He entered Tuesday’s contest with three goals and 15 assists through 40 games.
Johnston, 31, has two goals and 10 assists for the Ducks this season.