Gabriel Bourque appeared to give Colorado a 2-1 lead at 2:29 of the second period, but the goal was waved off because he played the puck with a high stick.
MacKinnon scored to make it 2-1 at 6:22 of the second on a wrist shot from the right circle. He received a pass from Rantanen, skated across the slot, and beat Rinne blocker side from a sharp angle.
Rantanen has had an assist on each of MacKinnon's 17 goals this season.
"[Rantanen] makes really good plays," MacKinnon said. "He's such a good passer. He finds me in a lot of quiet areas. On my second one, he knew I was going to cut to the middle. I was just waiting for him to see me. He's going to find me if I'm open, so it's a lot of fun."
Fiala tied it 2-2 at 9:06, redirecting a pass from Filip Forsberg past Varlamov's glove in the slot.
"Both teams had chances," Fiala said. "We had great chances in the last period, especially, I thought. It's one of those games."