With just over two minutes to play in the extra frame, and the game tied 2-2, MacKinnon picked up the puck near the blue line and got straight to work in the offensive zone.
The seven-time All-Star peeled away from some defenders then pulled a nasty drag move to open a lane in front of the net.
He finished with a top-shelf backhander to grab the extra point for the Avalanche.
"It was a lot of fun," MacKinnon said on the Avalanche TV broadcast after the game. "Scoring a goal like that at MSG, I was excited obviously."