Valeri Nichushkin and Samuel Girard scored, Gabriel Landeskog had two assists, and Darcy Kuemper made 23 saves for the Avalanche, the No. 1 seed in the Central Division who remain undefeated in the playoffs after a four-game sweep of the Nashville Predators in the first round.
Game 2 of the best-of-7 series is here on Thursday.
"I liked our game the whole night. I thought we were resilient there," Colorado coach Jared Bednar said. "Obviously we made a mistake on the penalty kill. We changed four guys, gave them one that was too easy. It is what it is.
"We've talked to our team all year long about being resilient and being mentally tough, and we came out and got right back to our game. Didn't capitalize on the power play, but just kept doing what we were doing throughout the course of the 60 minutes, and eventually we felt like we'd have a chance and break them down and get the winner. Our guys believed it. They worked hard for it, and I felt like they earned it tonight."
Jordan Kyrou tied it 2-2 for the Blues on a power play with 3:14 remaining in the third period when he stick-handled into the slot and shot from between the circles.
"I knew they were changing, and Justin] Faulk made a nice, quick [pass] up," Kyrou said. "I just took it in and saw a lane and shot it."
Ryan O'Reilly scored for the fifth straight game for St. Louis, the No. 3 seed in the Central. Binnington's 51 saves were an NHL career high in the postseason.
"I felt going into the game that we're right there, the way we've been playing," Blues coach Craig Berube said. "We need more guys to perform. That's really what it boils down to. And again, we've got to make more plays with the puck."
[RELATED: [Complete Avalanche vs. Blues series coverage]
Colorado outshot St. Louis 13-0 in overtime and 54-25 overall.
"'Mans' had a nice pump fake up top first that he doesn't get a whole lot of credit for, but that was really nice, and kind of got their forward to bite," Landeskog said. "He was able to get a shooting lane, and at that point I'm just trying to stand in front and kind of move out last-second."
O'Reilly scored on a backhand for a 1-0 lead at 6:25 of the first period after Cale Makar turned over the puck in front of the net.
Nichushkin tied it 1-1 at 3:14 of the second period on a rebound off a Mikko Rantanen shot.
"[Nichushkin's] been so good for us and he just keeps finding ways to be super effective for us, scoring big goals," Landeskog said. "Even when he's not scoring, he's contributing in other ways."
Girard gave Colorado a 2-1 lead at 11:32 of the second on a shot from the point. It was his second playoff goal in 42 games and first since Aug. 19, 2020.
"He had a great night," Bednar said. "He was involved in skating and in our offense right out of the gate. If I cut the scoring chances up, he's going to be a part of a lot of them. I thought he was really good tonight."
