MacKinnon gave the Avalanche a 1-0 lead on a power play at 2:43 of the first period, one-timing a feed from Jonathan Drouin.
Josh Norris tied it 1-1 at 15:13 when he one-timed Batherson’s backhand pass past a sprawling Georgiev.
Ridly Greig gave the Senators a 2-1 lead just 15 seconds later at 15:28. Dominik Kubalik tipped a shot from the point, and the puck rolled up and over Avalanche defenseman Devon Toews and off Georgiev before landing on Greig’s stick for the tap-in.
MacKinnon tied it 2-2 with a snap shot from between the circles that went under the left leg of Korpisalo at 18:28. It was MacKinnon’s 300th NHL goal.
“I think [it’s] the best [I’ve seen], probably, the way he's playing and skating and making plays and being hard to play against and defending hard,” Rantanen said of MacKinnon.
Jacob Bernard-Docker put Ottawa back in front 3-2 at 1:32 of the second period with a slap shot from the blue line that went off Colorado defenseman Cale Makar and got between Georgiev’s pads.
Batherson extended the lead to 4-2 at 14:47 when he corralled a cross-zone pass from Vladimir Tarasenko and fired it in far-side from the left face-off circle.
Rantanen cut it to 4-3 on a power play at 19:43 with a shot from the right circle.
“I was looking at the crease and I saw the goalie was scrambling a little bit,” Rantanen said. “I didn't even look at the net. I just tried to shoot it, and he wasn't in his position yet, so it was good to hit the net and score.”