That trade for Casey Mittelstadt looks pretty good so far.

Mittelstadt had three assists, including setting up the go-ahead goal with 6:31 left, and the Colorado Avalanche shook off a few minutes of lackluster hockey in the third period Sunday night to defeat the Ottawa Senators, 5-4, at Ball Arena.

It’s the Avs’ fifth straight win since starting the season 0-4. It’s also back-to-back three-point games for Mittelstadt, who joined the club before the trade deadline last season from Buffalo and signed a three-year contract this offseason.

Mittelstadt earned the primary assist on all three goals. He’s up to five goals and 12 points in nine games, and hasn’t played a minute yet this season with the two guys who will eventually be his wings — Artturi Lehkonen and Valeri Nichushkin.

He found Logan O’Connor in front of the net to make it a 3-2 game. Ross Colton continued his scoring tear to start the season with his eighth of the season 90 seconds later. Nathan MacKinnon added an empty-netter with 1:15 left to seal the win.

After Colorado had bottled up Ottawa for nearly 50 minutes, the Senators scored twice in 2:08 to even the score at 2-2. Brady Tkachuk had the first one, after a Tyler Kleven shot from the right point went wide. The rebound off the boards behind Justus Annunen came right to Tkachuk at the left post for a tap-in with 10:45 left in the third.

That was at the end of a shift where the Avs looked uncharacteristically a step behind after being in control for most of the night before that. Ottawa kept pushing and found another similar goal with 8:37 left. Nick Cousins put home the rebound of a shot from the left point after getting position on Colton near the right post.

Nikolai Kovalenko’s first NHL goal came with 7.8 seconds left in the first period to give the Avs the lead. Kovalenko found a spot in the slot to post up during a 6-on-5 because of a delayed Ottawa penalty, and Mittelstadt found him for a one-timer.

MacKinnon had the secondary assist on Kovalenko’s goal. He thought he had scored a goal earlier in the period, but it was waved off for goaltender interference after Mikko Rantanen bumped Anton Forsberg as he was falling down near the left post.

Forsberg was at the center of some quirky drama in the second period. He needed repairs done to his skate, but the first time it took so long that the officials made Ottawa put Linus Ullmark in until the next stoppage in play. Forsberg came back in, but then had to exit a second time for more skate repairs. He eventually returned, so the Senators made four goalie changes during the period.

The Avs closed the second the same way they did the first — with a goal in the final minute. Josh Manson skated from the right point toward the middle of the ice and flung a harmless-looking backhanded shot at the net. Forsberg didn’t track it well, and had no idea where it was as it trickled behind him and into the net.