Dunn took a puck to the face on a point shot from Sharks blueliner Brenden Dillon midway through the opening period that left him with a bloody mouth.
The team announced during the second stanza that Dunn wouldn’t return to the game.
The 22-year-old, after skating to the bench on his own, appeared to be in some discomfort as he needed assistance to his team’s locker room.
Dunn had an impressive seven points in 15 playoff games prior to Wednesday’s injury. It’s unclear at this time what Dunn’s status for Friday’s Game 4 in St. Louis might be.