Brock Nelson scored twice for the Avalanche (33-5-8), who lost at home in regulation for the first time this season (19-1-3). Mackenzie Blackwood made 23 saves.
“There were no positives. There really weren’t,” Colorado coach Jared Bednar said. “I hated that game from start to finish, pretty much. And then we get slightly better in the second period, and OK at the start of the third, but we didn't do enough to win the hockey game. So there's nothing I liked.
“We got to do better than that. That was not even close to the standard of hockey that we want to play.”
O’Reilly scored to make it 1-0 Nashville at 30 seconds of the first period when he went forehand to backhand at the top of the crease to score bardown in the right corner of the net.
"I'm just cutting in the slot there, trying to be a threat,” O’Reilly said. “And Fil just his possession. Makes a great play to me going to the middle, and I just, from where it was, wanted to go backhand. And I was just able to get it up, which was lucky for me.”
Nelson tied it 1-1 at 1:24 off a rebound of Brent Burns' point shot at the top of the crease, reaching behind his back to backhand the loose puck through the five-hole on Saros.
O’Reilly was credited with a goal for a 2-1 lead at 7:32 when his centering pass to Evangelista was deflected five-hole by Avalanche defenseman Samuel Girard. O’Reilly was below the goal line, off the right post, when he tried to feed Evangelista across the crease.
“It's awesome,” Forsberg said of O’Reilly, who played for Colorado from 2009-15. “He does everything. He's first out the door on the penalty kill. He's taking all the big face-offs and clearly producing as well. Leads the team in points, and then big game for him against his old team. It's fun to watch.”
Nelson scored his second goal to tie it 2-2 at 11:16, redirecting Josh Manson's point shot with the shaft of his stick. Nelson was sliding off the top right of the crease and put the puck far side past the blocker.
“Funny game today, where we come out of the first even and we weren't great,” Nelson said. “Second, play quite a bit better and have quite a few more Grade-A looks and chances, and we somehow find we're down two.
“We weren't at our best, especially early, but I don't know that there's cause for concern and panic.”