For the first time out, the Rangers’ new-look power play was pretty impressive. In fact, Mika Zibanejad scored twice with the man-advantage in the first period Thursday night.

But their defense was exposed numerous times by the quick transition offense of the Colorado Avalanche, who beat the Rangers in the season opener at Madison Square Garden, 4-2, as Semyon Varlamov, with 37 saves, outplayed Henrik Lundqvist in the nets.

Kevin Shattenkirk had an assist in his Rangers debut but was a minus-3 along with defense partner Ryan McDonagh.

Coach Alain Vigneault knew the Rangers would be a little unsettled, mentioning on Wednesday that it would take “10 to 20 games” to sort out roles and the roster. That timeline may have to be shortened.

Colorado was the worst team in the NHL last season and was beaten twice by the Rangers by a combined score of 10-4. It doesn’t get any easier for the Rangers, who will visit Toronto on Saturday. The swift and talented Maple Leafs scored seven goals on Wednesday.

Despite showing a lot of energy, the Rangers fell behind in the first period. Matt Duchene, the subject of trade rumors, knocked a rebound past Lundqvist at 5:29. The Avalanche followed that on the power play at 10:53 when Mikko Rantanen beat Lundqvist high to the glove side off a cross-ice pass from Nathan MacKinnon through Jimmy Vesey.

advertisement | advertise on newsday

Lundqvist, who is 20 pounds lighter than the heaviest he has been in his career, made his 12th consecutive start in an opener.

The Rangers fell behind 3-2 on a late second-period goal by Tyson Barrie, who was being chased by Pavel Buchnevich and beat Lundqvist. The chasing was a familiar sight through two periods as the Rangers continually had forwards trapped in the offensive zone.

Shattenkirk, who assisted on a power-play goal in the first period, said he was stung by the loss but thought “we did a great job of sustaining pressure, but when we turned the puck over, the problem we had was when our guy tried to force a play. Sometimes we [the defense] have to stay back and be more patient.”

Said Lundqvist: “Their speed and transition game, that’s where they really hurt us, in the odd-man rushes. In the third, we definitely had our chances to tie.”

Zibanejad, who admits to having confidence problems when he battles a scoring slump, was the best Ranger on the ice. He finished with eight shots, and a couple of Grade-A chances were denied by Varlamov. Zibanejad also won 16 of 24 faceoffs.

When Derek Stepan was traded to Arizona on the eve of the NHL Draft in June, the immediate question was whether Zibanejad, the 24-year-old who had his first Rangers season undermined by a broken leg, could handle being a No. 1 pivot. So far, so good.

On Thursday, Zibanejad, who missed some time in the preseason with a flu bug, looked healthy and determined, scoring twice in 2:30 late in the first, one on a wrister from in front and the other a sizzling one-timer from the left circle.

Lundqvist was pulled for an extra skater with 1:30 to play, and although the Rangers worked on the six-on-five format during recent practices, it didn’t click. Gabriel Landeskog scored into the empty net with three seconds left to seal it.

“We were working pucks back and making the most of our chances,’’ Zibanejad said. “I think we created some good momentum from it. We just have to take it a step further and score one when we really need it.”