The script felt like total fiction, a dream made up for a college sophomore and a No. 8-seeded playoff team who played in different countries 24 hours earlier.

Defenseman Cale Makar skated in the NCAA championship game for UMass in Buffalo on Saturday while the underdog Avalanche was preparing for Game 2 of its first-round series at Calgary.

So what unfolded in Game 3 at the Pepsi Center had to have seemed surreal to the Avalanche and its sellout crowd Monday — and particularly for the 20-year-old Makar.

Making his NHL debut in the Stanley Cup playoffs, Makar played regularly at even strength. He ran the No. 2 power play unit. He gained enough trust to play in a 4-on-4 situation. And, yes, he scored his first career NHL goal with his first shot in the league in a dominating first period that carried the Avs to a 6-2 victory and 2-1 series lead over the Western Conference’s top-seeded Flames.

The Avs outshot the Flames 56-29 and never let off the gas in a game that became chippy in the third period.

“We had good pace to our game and good execution. To me, the difference in the game was special teams,” Avs coach Jared Bednar said. “I thought (Makar) was good. Right from the get-go he was involved. He looked calm, cool and collected.”

Superstar forward Nathan MacKinnon got things going with two power-play goals before he dropped the puck for Makar on an offensive rush late in the first period. Makar collected the puck, drove to the net, fought off a defender and scored with a wrist shot to give Colorado a 3-0 lead.

The Pepsi Center was loud all night — but never as much as when Makar scored.

“It’s a lot of excitement, a lot of different emotions,” Makar told the visiting network Sportsnet during the first intermission. “Nate (MacKinnon) made a really good pass there, a drop. I was able to get inside the ‘D’ and go five-hole. It’s a great group of guys and they’ve accepted me really quickly.”

He added: “I don’t even know what (Nate) said (after the goal), it was so loud. A special moment and I was glad I could help this team.”

Forty-three seconds after Nieto’s goal, the Flames’ Sam Bennett scored a power-play goal on the same penalty kill. But the Avs got the momentum back with Mikko Rantanen’s goal to regain a four-goal edge heading into the second intermission.

MacKinnon finished with a game-high three points.

His power-play goals came at 8:26 and 13:34 of the first period — the first with a quick wrist shot from the right circle and the latter with a one-time slap shot from the left circle. Rantanen, Nieto and defenseman Erik Johnson each had a goal and an assist.

MacKinnon, the Game 2 hero with his overtime tally, now has three goals and four points in the series.

“It’s my job, stepping up in the playoffs,” he said. “Like I said before, my legs feel good. I could play all night.”

Goalie Philipp Grubauer was again “Gruuuuby” throughout the game — hearing the Pepsi Center chants on each of his saves.

Footnotes. Colorado entered the game 0-of-8 on the power play in the series but scored on two of its first three man-advantage opportunities, finishing 2-of-8. The Flames were 1-of-6 on the power play. ... The Avs tweaked their lineup late in the day, adding forward Sven Andrighetto to replace Derick Brassard, who was ill. Makar replaced Sam Girard, who sustained an upper-body injury late in Game 2. The Avs say Girard is day-to-day and he was seen looking healthy in the hallway before the game.

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