With under 10 minutes to go in the first period, Simmonds went to hit McDonagh, and the Rangers D-man cross-checked Simmonds in the face.
Simmonds responded with a slash, and then punched McDonagh, who stayed down on the ice before leaving the game to be looked at.
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In the end, Simmonds received a match penalty for intent to injure, and was thrown out of the game, while McDonagh got two minutes for slashing, and two minutes for high-sticking.
The Rangers received a one-minute power play after the teams played 4-on-4 for four minutes. The team announced later that McDonagh would not be returning to the game.
Under Rule 21 regarding match penalties, Simmonds will be suspended indefinitely until commissioner Gary Bettman reviews the play.