DENVER -- Anders Nilsson was added as insurance when he was acquired from Edmonton on Feb. 26.

St. Louis cashed in his policy Sunday, and the goaltender came through when starter Jake Allen went down.

Nilsson stopped 19 of the 20 shots he faced in the last 40 minutes, and the Blues inched closer to first-place Dallas with a 5-1 win over the Colorado Avalanche on Sunday night.

David Backes, Colton Parayko and Magnus Paajarvi scored in a decisive three-goal first period, and Alex Pietrangelo and Troy Brouwer also had goals for St. Louis.

The five goals helped ease the pressure on Nilsson, whose only action since he joined St. Louis was 27 minutes at Calgary on March 14.

"I felt better than I thought it was going to be," said Nilsson, who was pressed into action with Brian Elliott back in St. Louis. "The guys in front of me did a good job. The shots that came were mostly from the outside. It was fun to play. It's been a little while."

Nilsson came on after Allen suffered an undisclosed injury late in the first. He played the rest of the period but stayed in the locker room. Allen, who missed 17 games earlier this year with a lower-body injury, finished with 11 saves.

"I'm not even sure what it is," Blues coach Ken Hitchcock said. "We'll have a better evaluation in the morning. Hopefully it's day to day."

St. Louis (47-23-9) moved within two points of first place Dallas in the Central Division after the Stars lost at Anaheim on Sunday night.

The Blues, who are four points ahead of third-place Chicago, have played one less game than Dallas.

"We know what's in front of us, we know what's behind us," Pietrangelo said. "The biggest thing is worrying about ourselves. We know if we play the way we can we're going to put ourselves in a good position."

Duchene scored his 30th goal late in the third for the Avalanche and Calvin Pickard had 23 saves in relief of Semyon Varlamov, who was pulled after allowing three goals on 14 shots in the first period.

Colorado's hopes for a late-season push to make the playoffs are almost over. The Avalanche (39-36-4) trail Minnesota by five points with three games remaining, and another regulation loss or a Wild victory will eliminate them for the second straight season.

The Wild lost in Winnipeg on Sunday.

"I saw Minny lost again, so it's disappointing not to come away with two there and gain a little ground," Matt Duchene said. "The good news is we're still in it, we have a chance here."

The Avalanche haven't helped their cause, losing their fourth straight at home. Colorado is 17-19-4 at Pepsi Center this season and has been outscored 17-5 in those four games.

"For some reason we're in a funk at home and we're struggling winning some hockey games," Colorado coach Patrick Roy said. "It's not the type of hockey we want to play. We need to learn how to win. We need to change the mindset. We have a losing mindset right now. We have to find ways to believe more in ourselves."

The Blues struck early to build a 3-0 lead after the first period. Backes' 21st goal of the season, on the power play, came on a 2-on-1 with Tarasenko at 5:30.

Paajarvi made it 2-0 when he whacked at the puck a couple of times and put it between Varlamov and the post at 8:56. It was his third of the season.

Parayko finished the rally with a one-timer from the top of the right circle that went through Varlamov's legs at 16:09.

"The last game we had a good push in the third and we carried that over to the start," Pietrangelo said. "We needed a good response and the response was what we needed.

Calvin Pickard replaced Varlamov to start the second period but St. Louis was able to expand the lead on Pietrangelo's seventh goal of the season at 3:26.

Duchene scored at 15:46 of the third but Brouwer got his 17th on an empty-netter with 2:55 left.

NOTES: Avalanche D Nikita Zadorov was out of the lineup with a concussion suffered in Friday's loss to Washington. Zadorov was hurt when he was hit by Capitals RW Tom Wilson. ... Blues D Jay Bouwmeester (upper-body injury) and C Robby Fabbri (lower body) resumed skating. D Carl Gunnarsson was back after missing three games with a lower-body injury. ... Avalanche C Nathan MacKinnon missed his seventh straight game with a knee injury. He still has not resumed skating and could be done for the season. ... St. Louis G Brian Elliott did not accompany the team to Denver for the one-game trip.