Late in the third period, the Bruins were cruising to a Game 3 win, but the Blues had pulled their goalie (again) and were peppering the net with shots.
One of those shots ran into Charlie McAvoy; more specifically, it ran into the inside of his left knee:
As you can see from the clip above, McAvoy’s block eventually led to a Noel Acciari goal, but it also led to a whole lot of discomfort for McAvoy.
McAvoy skated to the bench doubled over in pain, remained doubled over on the bench, then headed down the tunnel after the empty-net goal.