Alexander Steen scored his 20th of the season and Jaden Schwartz also had a goal for the Blues, who have won five straight. It was their first victory in Colorado since April 12, 2009.
"I can't tell you the last time we won in this barn, so obviously coming here, it's big getting two points," said Chris Stewart, who was playing for Colorado when St. Louis last won in Denver. "I think I was on the receiving end last time this team won in this barn, so it's a big two points."
The Blues lead the NHL with 18 wins more than a quarter of the way through the season.
Colorado coach Patrick Roy was angry after the game with what he considered a double standard. Roy, hired by the Avalanche from the Quebec Major Junior League last summer, took some criticism earlier this season for talking to opposing players during the game.
He took issue Wednesday with St. Louis coach Ken Hitchcock.
"I was very mad at the end because I've been jabbed by different coaches around the league, especially Hitchcock when he said that's junior, stop talking to players and talking to the referee," Roy said. "But I saw a guy on the other side who was talking to players and was also talking to the referee. He got the referee even (angry). Seems to me there's different rules for everybody in this league.
"I guess the old guys are allowed to do whatever they want and I guess us, because we're younger, we can't say anything. I'm a little (mad) about that."
Colorado's 17-5-0 start was a franchise best this deep into the season, but the Blues have been the better team lately. They have won 10 of 12 and earned points in 11 of those games.
"We are sticking to the way we play. We have been for the last little while," Steen said. "Pucks are bouncing our way, we are taking care in our own end and our goaltending has been phenomenal."
St. Louis is 4-1 in one-goal games during its recent run and has averaged 3.4 goals.
"Our 5-on-5 play is getting better and our special teams have really carried us," Hitchcock said.
One of the wins in that stretch was a 7-3 victory over Colorado on Nov. 14, which came in the middle of a three-game skid for the Avalanche.
St. Louis dominated that game from the start of the second period, and that continued Wednesday.
The Blues had the first seven shots, and goals by Backes and Steen in the first 6:10 of the game gave them a quick two-goal lead. Backes scored when he redirected T.J. Oshie's pass on a rush 2:46 into the first period. Steen made it 2-0 with a power-play goal, which tied him with Washington's Alex Ovechkin for the overall NHL lead.
"We haven't had good history in this building the past few years, so we needed to set the tone," Backes said. "Oshie makes a great pass and I found a piece of it and it found a hole."
After being outshot 9-1 to that point, Colorado pushed back and got on the board when Bordeleau stuffed in a rebound midway through the first. The Avalanche had several chances to tie it, but Schwartz's short-handed goal with 1:48 left in the period made it 3-1 and stopped Colorado's momentum.
"We lost the game in the first 10 minutes," Matt Duchene said. "If we played a little better in the first 10 there, even giving up that shorty late in the first period there we go into the next period with a 2-1 deficit, it's a different game."
The Avalanche failed to mount a comeback in the final two periods. They were held to 14 shots in the last 40 minutes, with four coming in the final 5 minutes of the game. They had two on a power play and two more after pulling Varlamov for an extra skater, but Stewart sealed it with an empty-net goal with 1:44 left.
"In general, we played a really sound game," Hitchcock said. "We managed the puck properly, we just did a lot of things good. We had a lot of guys on top of their game."
Blues C Derek Roy had two assists. ... Avalanche C Paul Stastny missed the game due to back spasms. ... Duchene returned to the lineup after missing three games with an oblique strain. ... Steen has 99 goals as a member of the Blues. ... St. Louis' short-handed goal was its first of the season. It also was the first short-handed goal allowed by Colorado.
Copyright by STATS LLC and The Associated Press
DENVER, CO - NOVEMBER 27: Goaltender Semyon Varlamov #1 of the Colorado Avalanche talks with Vladimir Tarasenko...