UNIONDALE, N.Y.—Islanders center John Tavares scored three goals Saturday night in a 4-2 victory over the New York Rangers. The third was an empty-net goal, so for the purpose of understanding the player Tavares is becoming, let's consider the first two.

Goal No. 1: Rangers goaltender Henrik Lundqvist makes a pad save on a shot by defenseman Mark Streit, but the rebound ends up on the backhand side of Tavares's stick. Tavares pivots on his right skate and, rather than sweeping the puck immediately back into Lundqvist, keeps...