MacKinnon, who played his second game since returning from an upper-body injury, scored 25 seconds into the first period to make it 1-0, beating Thompson blocker side from the right face-off circle.
"I'm getting more comfortable. I'm seeing some plays out there tonight a little bit better," MacKinnon said. "There's no quit in our room, which is a good thing moving forward. We just need to get healthy."
Amadio tied it 1-1 at 17:02 when he redirected Nicolas Hague's shot from the point. The goal came moments after Rantanen hit the crossbar on an open net.
"Amadio goes up, he's been real hot on [the top] line. He's a guy that can add some offense, so that's a nice find for us as well," Cassidy said. "I think to sustain seasons when you have as many guys as we have out -- a lot like the [Avalanche] right? -- you need guys to get in there. (You) need your top guys to produce and other guys to sort of follow. Your leaders lead, your followers follow, and I think we've seen that with our group."