Brock Nelson got his standing ovation.

The Islanders got their two points.

Maybe that wasn’t how Nelson envisioned his return to UBS Arena going, and who could blame him given that the Avalanche had lost just once in regulation all year and once in their last 13 games.

But a night that started out being about Nelson’s first game back on Long Island became about the Islanders getting their best win of the season so far, beating a juggernaut Avalanche team 6-3 on Thursday night to finish a rocky seven-game homestand strong.

It was just over a couple of weeks ago that the Islanders thought they played their best game of a seven-game road trip in Denver, only for it to be the only game they lost on that swing.

The Islanders celebrate a goal during their Dec. 4 win against the Islanders. Robert Sabo for the NY Post

They will feel more than validated by what they saw Thursday, when a lineup without Jonathan Drouin — scratched after taking warmups due to a lower-back injury and called day to day — not only hung around with the current Stanley Cup favorites, but never trailed.

“Like I said to [the team] before the game, I believe that if there’s a team that could surprise them, it’s us,” coach Patrick Roy said. “The way we’ve been playing, we’re playing really good hockey lately.”

Matthew Schaefer and Ryan Pulock, asked to take on the matchup against Nate MacKinnon, Martin Necas and Artturi Lehkonen, hung tight, with the rookie continuing to prove he is up for any challenge.

Ilya Sorokin was terrific in making 35 saves, standing up to numerous barrages around the crease to continue a brilliant run of form.

Hanging onto a two-goal lead for nearly the entire third period after Lehkonen cut their lead to 5-3 and absorbing all the requisite pressure, the Islanders never caved.

Again and again, they stopped Colorado at the blue line and forced the Avalanche back 200 feet.

Simon Holmstrom battles for the puck during the Islanders’ Dec. 4 win against the Islanders. Robert Sabo for the NY Post

Even when Scott Mayfield took a tripping penalty at 16:42 of the last period, allowing the Avs to skate six-on-four, the Islanders promptly killed it off, and seconds later, Casey Cizikas sealed the game with an empty-netter.

“I think it’s just desperation,” Adam Pelech said. “It’s tough. They got a ton of talent. Six-on-four, it’s really a battle. You really gotta sacrifice, block shots, be in the right positions, be disciplined with your positioning. It was huge for us.”

Mathew Barzal, who has disappeared across portions of the last couple of weeks, including Tuesday’s win against Tampa Bay, had his best game of the season, bar none.

He was incisive, engaged and creative as ever.

He pulled up and delivered a cross-ice feed for Anders Lee’s one-timer that made it 2-0 at the 18:20 mark of the first — coincidentally, Lee’s goal tied him with Nelson for fifth on the franchise’s all-time goals list — then with the Islanders needing to claw back some momentum late in the second, he skated past two defenders and finished on his backhand to make it a 5-2 game.

“He was outstanding tonight,” Roy said. “… When Barzy plays well defensively, for some reason, it helps his rush and he gets the puck faster and gets into the rush and generates. That’s how he scored the first goal, the pass across he made to Leesy. He had a strong game.

Ilya Sorokin protects the net during the Islanders’ Dec. 4 win against the Avalanche. Robert Sabo for the NY Post

“I will say this: You don’t beat the best team in the NHL if everyone’s not playing.”

After Valeri Nichushkin and Necas had cut a 4-0 lead to 4-2 with goals 1:25 apart midway through the second, Barzal’s goal was the one the Islanders needed badly.

Earlier in the second, Bo Horvat and Pelech had scored just 1:01 apart to double a 2-0 lead, both goals coming as a result of poor goaltending from Mackenzie Blackwood — Horvat’s off a rebound, Pelech’s from a shot from the left circle that should have been easily stopped.

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All four lines competed across both zones in an effort that saw Kyle MacLean net the fourth line’s first goal of the entire homestand to open the scoring 5:56 into the game.

The Avalanche, though, are never out of a game, and they were not out of this one.

This is a win the Islanders can hang their hats on and, combined with Tuesday’s win over the Lightning, a win that will validate the self-belief they kept intact through a 1-3-1 start to this homestand.

Especially if Drouin is out through this weekend, the Islanders are not out of the woods yet.

But they are right in the mix in an Eastern Conference where just six points separate first place from 12th.

And after Thursday, you would be silly not to take them seriously.