St. Louis (43-14-6) stretched its lead to five points on third-place Colorado (41-18-5) in the Central Division (92-87) and has a game in hand.
This game was a lot more competitive than the first two, which the Blues won by a combined score of 11-4.
"I thought both teams played hard," St. Louis coach Ken Hitchcock said. "It was a good hockey game. I thought we were really focused and good. Their first goal gave them some energy and we started shoveling the puck rather than skating with it. It was quite a hockey game. Both teams are playing at the top of their game.
"The building's so loud, I'm not sure if it's the new [video board], but it feels like you're in a playoff game every time. It feels like there's 100,000 people in here because it's so loud. Both teams knew what was at stake and played their hearts out."
The Avalanche pulled goalie Semyon Varlamov with 2:33 to play and had some good chances but couldn't send the game to overtime.
"I thought both teams played really well," Avalanche coach Patrick Roy said. "I thought it was a hard-fought game and was very entertaining for our fans. Our guys battled until the end and we had some good chances 6-on-5. We showed a lot of good things out there.
"It was a lot different than the last two games we played against these guys. We were physical, we had some good body checks. Sometimes, unfortunately, you're not always rewarded for the way you play. I thought we had better chances than them. I thought we deserved as much to win."
Patrik Berglund gave the Blues a 2-0 lead at 3:53 of the third period with an uncanny shot from the right circle. He spun around and shot the puck between Avalanche defenseman Nate Guenin's legs and past Varlamov's glove for his fourth goal in four games.
The Avalanche, who haven't been shut out this season, made it 2-1 with 11:03 to go on a goal by PA Parenteau. Matt Duchene moved from the side of the net and cut inside Blues forward Steve Ott for a shot. Goalie Ryan Miller made the save, but Parenteau banged in the rebound.
Miller made a save against Gabriel Landeskog with six minutes to play after a Blues turnover in their end. Landeskog was on his knees when he shot the puck off Miller's mask.
"When he fell to his knees I thought maybe he'd consider pushing it to a guy who was still up," said Miller, who made 26 saves. "He caught me in the eye right there. I was kind of fortunate he didn't pick a corner and he hit me. When he went down I was thinking pass and maybe I hesitated a little bit. Smart play by him to shoot it. Not really an attempted save."
Miller is 4-0-0 since arriving in a trade from the Buffalo Sabres a week ago Friday. He has allowed one goal in each of the past two games.
"It's been great to contribute," he said. "Things have really worked out in our favor. It's been good, a hard-working game, guys are playing honest hockey and they've gotten good results because of it."
Hitchcock said of Miller, "He just absorbs everything. He was good tonight. You need your goalie to win on the road. He absorbs all the shots. His whole disposition calms everyone down. There's a reason he's won so many games."
The Blues took a 1-0 lead at 7:03 of the second period on a goal by David Backes, who has six goals and five assists in his past nine games against the Avalanche.
T.J. Oshie sidestepped two Avalanche defenders as he skated down left wing and passed to Backes driving to the net for a shot Varlamov had little chance to stop.
"We were making a pretty good push in the second and finally we found it," Backes said. "[Oshie] makes an amazing play and slides it back door. I had the easy part on that one. You figure the first team that was going to find the back of the net was going to have a great chance to win this one, and that was the case."
The Blues are 35-1-4 when they score first; the Avalanche are 31-1-3.
Backes' goal came 17 seconds after the Blues held the Avalanche to one shot on goal during a power play with Barret Jackman in the penalty box for interfering with John Mitchell. Landeskog hit the crossbar with a shot just before the advantage expired.
"There's always key moments in a game and [Landeskog] hit the crossbar and they go the other way and took the 1-0 lead," Roy said. "It was the difference after 40 minutes of play."
That and the fact Avalanche defenseman Jan Hejda hit the far post with a shot from the left point with 1:40 to go in the period.
The Avalanche went on their third power play 20 seconds after Backes' goal when Berglund was assessed a delay of game penalty for clearing the puck over the glass, but St. Louis' Alexander Steen had the only shot, one from the high slot that Varlamov stopped, one of his 23 saves.
The Blues outshot the Avalanche 2-1 while killing off three Colorado power plays.
"I think that was one of our weaknesses tonight," Parenteau said. "I thought the power plays have been really good lately moving the puck pretty well, but they played really good and we didn't. I mean, a power-play goal would've made a huge difference there and that's something maybe we have to address. I think we have to take advantage of our power plays, for sure."
Avalanche rookie forward Nathan MacKinnon didn't have a shot on goal and had his scoring streak stopped at 13 games. His usual center, Paul Stastny, sustained a back injury on his first shift in the opening minute of the game and didn't return. Stastny missed two games earlier this season because of back spasms.
"It definitely threw us off a little bit," said MacKinnon, who moved from right wing to center on a line with Landeskog and Jamie McGinn. "Obviously Paulie is a huge part of our team. We were juggling around at times. I thought as a unit our line could've been better. We created some chances at the end and I thought we deserved to tie it."