Here, finally, came a game in which the Islanders went up against a top-end opponent and checked just about every box, including that most important one: winning.

This was needed in every way, this emotionally charged comeback 4-2 victory over the Panthers on Sunday night at UBS Arena which saw the Islanders put together a four-goal third period to beat the defending Stanley Cup champions on the night Mike Reilly returned to the lineup following heart surgery and put a stretch pass across two zones onto Maxim Tsyplakov’s tape for the game-tying goal.

For the confidence of this club, whose sole win since trading Brock Nelson was a lacking performance at San Jose, for the playoff race in which the Islanders keep on hanging around, now four points back of the Rangers with a pair of games in hand, and for Reilly — whose recovery after more than four months out is nothing short of remarkable — this was sorely, desperately needed.

“It’s been pretty tough,” Reilly said after skating 14:16 and appearing as though he had not missed a beat despite months away from the game. “So I think to be back, it’s special. Obviously a lot of work into it. Some unknowns at times. All in all, good to be back.

“The goal was to get back before the end of the season. I’m glad that happened.”

Reilly’s presence, mere months after doctors found an abnormality with his heart — while he was recovering from a concussion — which required surgery to fix, made this night about more than hockey.

His career was never at risk, but that is the sort of thing to make anyone pause and take a beat.

To come back and play so soon, and to do so at a high level in an important game, is as much — and more — as anyone could have asked.

Even so, this was trending toward a fourth straight loss, and another game in which the Islanders’ goal scoring proved the decisive issue after trading Brock Nelson.

Early in the third period, after a third scoreless power play of the night, a “Let’s go Panthers” chant was heard at UBS Arena with the Islanders trailing 2-0 in a moment which threatened to be the wrong kind of emblematic.

Shortly thereafter, Marc Gatcomb put the Islanders on a pathway to making sure it would not be.

The fourth-liner took his own rebound off Tony DeAngelo’s initial shot and scored a wraparound goal to bring the Islanders within 2-1, giving them some badly needed momentum.

The lack of a fourth power play following what looked like a Gustav Forsling trip on Gatcomb ended up being a blessing in disguise for the Islanders, as just seconds later, Tsyplakov got free on the rush to score his first goal since December, tying the game at two off a feed from Reilly.

All of 17 seconds later, the Islanders were in the lead after Noah Dobson made a play straight out of his 2023-24 season, forcing a turnover in the neutral zone and taking the puck all the way before finishing past Vitek Vanecek for a 3-2 lead.

“We didn’t change our game,” captain Anders Lee said. “We didn’t press at the wrong time or do anything differently. We were getting the looks in the first 40 and controlling a little bit. We had possession and liked what we did in the O-zone. We needed to bear down on some chances.”

Indeed, the Islanders did control play throughout this one, recording 12 of the game’s 13 shots while failing to score over the opening 20 minutes before falling down 2-0 on a pair of greasy Florida goals.

It looked much like the overtime loss to Edmonton two nights prior, an everything-but-the-goals performance where the overriding question was whether the Islanders would break out of their scoring slump.

The lead they built in the third, though, held true despite a furious Panthers push at six-on-five, with Ilya Sorokin denying multiple scrambles at the crease before Simon Holmstrom’s empty-netter sealed the win.

“In the third, they had zero chances until that five-on-six,” coach Patrick Roy said. “And five-on-six, the goalie has a big role to play. He did in a great way.”

It’s easy to forget, a year after the fact, just how done and dusted the Islanders looked last season, as late in the year as early April.

That rally to the playoffs started against the Panthers, with a 3-2 comeback win in Florida which kicked off a 9-1-1 stretch over the season’s final 11 games.

Another comeback victory against Florida later, there is another rally to be had if the Islanders can grab it.