SALT LAKE CITY — As Mitch Marner and the Vegas Golden Knights celebrated their 5-1 win to close out their first-round series against the Utah Mammoth at the Delta Center, “Good Vibrations” was blasting in the dressing room.

Marky Mark and the Funky Bunch’s 1991 hit was a fitting tune. Vibes couldn’t have been better for Marner and his teammates on Friday night.

The star forward, who signed an eight-year, $96 million contract with Vegas last July, was a force in the close-out game. For all of the goals and assists he racked up over his nine years with the Toronto Maple Leafs — and there were a lot of them — the overwhelming narrative that followed him out of Toronto was that of an elite offensive playmaker who struggled to make the biggest plays in the biggest moments.

In his first opportunity to rewrite that narrative, in the first close-out game of the first playoff series with his new team, Marner delivered.

“It was his best game of the series,” Vegas coach John Tortorella said of Marner’s two-goal, three-point night. “He just looked comfortable.”

“Comfortable” wasn’t a word commonly associated with Marner in the playoffs in Toronto, especially as he got deeper into a series, but it was the perfect descriptor on Friday.

The pivotal moment of the game came in the final minute of the second period, with Vegas leading 1-0. In the shift prior, Golden Knights center Jack Eichel put the Mammoth through the wringer. He buzzed around the Utah zone, zipping passes to teammates and winning stick battles to prolong the attack.

Then, with Utah’s defenders exhausted and possession secured in the corner, Eichel skated to the bench to change. Marner jumped over the boards and curled into the high slot, where Ivan Barbashev fed him the puck. He wheeled around his defender with a quick crossover and unleashed a slap shot past Utah goalie Karel Vejmelka’s glove to extend the Vegas lead to two.

It was a clutch goal, and Marner’s first of the playoffs. It was exactly what he needed.

Marner was one of Vegas’ most impactful players through the first five games of the series. He used his speed to create space for his linemates and his hockey IQ and quick stick to kill off Utah’s chances with regularity. He had an assist in all but one game in the series, including shorthanded helpers on two critical goals by Brett Howden.

But for a player of Marner’s caliber, with his contract and his history in close-out games, the goals needed to come eventually.

“Mitchie has been doing a lot of the little things that people don’t understand,” Tortorella said. “Some small, little plays, but he had some big plays tonight that everybody can see. It was really good for him, for his confidence, going into the next series.”

Marner’s slap shot ended up being the game winner on Friday. He added another goal in the third period, finding a rebound in front of the Utah net and crushing it by Vejmelka to extend Vegas’ lead to three and ice the game.

It was Marner’s first multi-goal playoff game in more than three years. In one try, he has now scored as many goals with the Golden Knights in games where one team faces elimination as he had in nine seasons in Toronto. What can he glean from this performance to eliminate Utah?

“Trust yourself, and trust yourself in those moments,” Marner said. “Just trust yourself more, to shoot more. Find yourself in areas that you have more confidence to score.”

Marner was Vegas’ best player all night. In his 13 minutes of even-strength ice time, the Golden Knights held the edge in goals (2-0), shot attempts (17-8), shots on goal (10-3) and scoring chances (7-3), according to Natural Stat Trick. Of the 10 shots on goal, seven were taken by Marner — his highest total as a Golden Knight and the second-highest of his career in the playoffs.

“He was great,” said Vegas forward Colton Sissons, who scored Vegas’ third goal of the game. “I think tonight he was probably at his best. Obviously, he scored some nice goals for us, but he was just very impactful every time he was on the ice.”

The experience and championship pedigree in the Golden Knights’ dressing room helped draw Marner to Vegas last summer. Heading into free agency, he could’ve been wined and dined by teams across the NHL, but he chose to forgo that and immediately sign with Vegas on July 1.

The team’s traits showed up Friday night and throughout the first-round series.

“I think it helps having a veteran group,” Marner said. “It helps that this group has been through some adversity in past years, that it doesn’t really slow them down or back them off.”

The Golden Knights surrendered four straight goals to Utah in Game 4 to squander a 3-0 lead, but they didn’t flinch and came back to win in overtime. They trailed on three separate occasions in Game 5, but rallied each time before winning in double overtime.

“We’ve been here before,” said captain Mark Stone, who has played in 90 playoff games in his seven years in Vegas. “We don’t have the panic that maybe some teams do. We can calm ourselves pretty quickly.”

It’s a great environment for Marner to shed his playoff demons, whether those are deserved or not, and allow his talent to shine through. It’s only one series, but it’s the first step toward what Marner envisioned when he signed with Vegas.

“This is what I hoped for, for sure,” he said. “An opportunity to do something special.”

The Golden Knights will host the Anaheim Ducks to start the second round. The Ducks are a team built similarly to the Mammoth, with heaps of youth, speed and skill up front and veteran leadership on the blue line. It’s also a team, led by a Cup-winning coach in Joel Quenneville, that went 3-0 against Vegas in the regular season.

This game and the first-round series are far from the end of this story for Marner. As clutch as Friday’s performance was, the Mammoth aren’t exactly the most physical, tight-checking team in the NHL. Things are likely to get tougher for Marner and the Golden Knights against the likes of Jacob Trouba, John Carlson and Radko Gudas (if he’s healthy).

It’s the type of test Marner hoped to face when he came to Vegas.

“Like I said when I first got here, I knew it was a special group,” Marner said. “All four lines contributed throughout the series. There were different moments that we needed every line to step up and come up big, and every line did that. This is what I hoped for. There’s a lot more work, so let’s get the rest we need here and be ready for Anaheim.”