Tkachuk scored with a snap shot on a breakaway for his second goal of the game. He also had an assist.
"I was just thinking, 'Don't toe-pick,'" Tkachuk said. "I was trying to get the getaway boots going there a little bit. But overall, just happy with the outcome. It was definitely an exciting win tonight."
Tim Stutzle
had two goals and an assist, and Anton Forsberg made 26 saves for the Senators (6-15-1), who have won two straight games for the first time this season. They won 3-2 at the Carolina Hurricanes on Thursday.
"It was a good effort by our team," said Tkachuk, the Ottawa captain. "That's a good team, and now we've had good efforts against two top teams. We've put in some great efforts, but I believe that we have more."
Alex Newhook had a goal and an assist, and Nathan MacKinnon had three assists for the Avalanche (12-7-2). Jonas Johansson allowed four goals on 15 shots before being replaced early in the second period by Justus Annunen, who made 17 saves in his first NHL game.
"We don't want to play that type of way against anybody," Colorado captain Gabriel Landeskog said, "no matter where they are in the standings, knowing that the second half of the year and down the stretch and in the playoffs it's going to be 2-1 and 1-0 and 2-0 games in the playoffs. We know that we just can't be giving up that many goals."
Devon Toews scored with a slap shot from the point for the Avalanche to tie it 5-5 with 1:20 remaining.
"It's a big point," Colorado coach Jared Bednar said. "I don't love the game from us, but I love the resolve to stick with it and believe that we can come back and get the job done. It's not easy down three [goals] against anybody. It's not easy and it didn't come easy for us tonight. We didn't have a lot of power plays and we just kind of stuck with it."