Anthony Beauvillier #18 of the Islanders celebrates his second period...

Anthony Beauvillier #18 of the Islanders celebrates his second period goal against the Buffalo Sabres at NYCB Live's Nassau Coliseum on March 30, 2019, in Uniondale, New York. Credit: Jim McIsaac

Fans of the Islanders understandably will spend Sunday thinking deep playoff thoughts.

What team will they face, and where? (See you soon, Sidney Crosby?) Which goaltender will start? How far can they go?

For what it’s worth, it says here they could go far indeed, no April foolin’.

All of that is as it should be. But let us take a moment before March ends and the regular season fades into memory to appreciate what the Islanders have done.

The capper came Saturday night at NYCB Live’s Nassau Coliseum, where they secured a berth in the Stanley Cup tournament with a 5-1 rout of the overmatched Sabres.

It was the first time they clinched a postseason spot on home ice in 17 years, a moment thoroughly enjoyed by a raucous, happy crowd.

When it was over, players gathered at mid-ice to raise their sticks in tribute as the fans — most of whom stayed to the end — rose as one.

“I was having goosebumps saluting the fans there,” said Anthony Beauvillier, who scored two goals. “It’s just crazy how loud they’ve been all year. Everybody’s happy. They’re happy, we’re happy, and it’s going to be lots of fun [in the playoffs].”

From a spring 2019 perspective, none of this came as a surprise, given what has unfolded over the past six months, including a stint in first place in the Metropolitan Division.

But a time traveler from October likely would have been shocked.

ESPN’s preseason power rankings placed the Islanders 26th in a 31-team league. Its Canadian counterpart, TSN, was more optimistic, rating them 25th.

It made sense, even with the arrivals of Lou Lamoriello in May and Barry Trotz in June, what with John Tavares departing in July and most of the roster returning after having made a mockery of defense in 2017-18.

And yet here we are. The Isles underwent a radical transformation on defense, got sharp goaltending from Robin Lehner and Thomas Greiss, and made up for a lack of elite scoring punch with a balanced attack.

They have eight players with between 15 and 28 goals.

Oh, and they did it while calling two arenas home, a profoundly unconventional arrangement that will continue in the playoffs if they reach the second round.

It was the first time they clinched a playoff spot before the end of March in 29 years.

“We believed we could do it, and we did it,” Matt Martin said. “The validation is for ourselves and our fans and the people who supported us.”

The fact that it happened at the Coliseum, a building the Islanders thought they were leaving forever four years ago, made it even more satisfying and a bit surreal.

“Two years ago, if you’d asked me if this would happen, I would have told you ‘no chance,’  ” said Martin, who left the Islanders for two seasons in Toronto before returning. “It was special to do it here. Our fans have been unbelievable all season supporting us. They brought the energy.”

The good vibrations were evident from the start, with fans getting into it early and often with generic Islanders chants that later evolved into “We want the playoffs!” and “Bar-ry Trotz! Bar-ry Trotz!”

Asked about the chant, Trotz said, “It’s very nice, but they can cheer the players. They’re the ones playing .  .  . I’m just that pretty face behind the bench.”

The players’ reaction in the locker room was relatively subdued. “It’s awesome,” captain Anders Lee said. “We’ve been up in the standings for quite a while, so this doesn’t feel like a surprise or that we should be jumping for joy.”

In the big picture, that is true. The goal is winning the Cup, as always. So no, Saturday was not the finish line of the marathon. But it was a mile marker worth celebrating.

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