The Colorado Avalanche better figure things out at home if they’re about to clinch home-ice advantage throughout the Western Conference playoffs.

That clinching, however, did not happen on Sunday evening.

Robert Thomas completed the hat trick with 2:50 remaining in the third period, taking advantage of the Avalanche getting caught up ice late and giving the Blues the 3-2 lead that they held on to for the victory. Jimmy Snuggerud toe-dragged around Martin Necas and fed Thomas, who was wide open on the back door for his third goal of the night.

It’s safe to say Necas being the last guy back was not in the game plan for Colorado.

“It was a tight game,” Nathan MacKinnon said. “Got to watch that last goal. I don’t know why Marty’s playing (defense). Tough way to lose.”

The Avalanche had plenty of chances to break this game open. Martin Necas had a breakaway on the first shift of the game that Joel Hofer stopped, and MacKinnon had a handful of glorious scoring chances that he failed to capitalize on.

Creating offense wasn’t really the issue, though. Less than 24 hours after playing one of their best defensive games of the season, the Avalanche were much looser defensively, giving up several odd-man rushes, three of which the Blues capitalized on.

The inconsistency from game to game comes down to one thing for the head coach.

“It’s strictly commitment. That’s all it is, nothing else. Commitment to play the right way,” Jared Bednar said.

The Avalanche have now lost six of their last seven games at Ball Arena, a place they’ll be spending more time at when the playoffs get underway. They’ve still got three more home games before the end of the regular season to get some positive momentum going heading into the postseason.

Blues 3, Avalanche 2

What happened: St. Louis looked like the more desperate team as they keep their slim playoff hopes alive.

What went right: Parker Kelly scored his 20th goal of the season, a crazy accomplishment for someone who had never scored more than eight in a season prior to this campaign.

What went wrong: Valeri Nichushkin played until the buzzer on Saturday, but was a surprise scratch against the Blues with what the team called an upper-body injury. It sounds like the Avalanche are just playing it safe, though. “Day-to-day,” Bednar said. “He’s probably a possibility, even for Tuesday. We’ll just see how he feels the next couple of days.”

Avalanche goal scorers: Kelly (20), Burns (12)

Blues goal scorers: Thomas (19, 20, 21)

Between the pipes: Mackenzie Blackwood played well and didn’t get a whole lot of help on any of the goals scored by the Blues. He finished with 25 saves.

What’s next: The Avalanche play the Blues again, this time in St. Louis, on Tuesday at 6:30 p.m.