The Islanders have not rolled over often this season.

But in their first game back from the Christmas break, that’s exactly what they did.

The Penguins walked into UBS Arena and whipped the Islanders, blowing them off their home ice to the tune of 7-0 in what was easily the worst all-around effort the home team has put up this season and the worst loss the franchise has suffered in seven seasons.

“The way nights are gonna go sometimes, they don’t always go your way,” captain Anders Lee said. “But the tenacity, the bite, the what-it-takes to stop something like that wasn’t there.”

These Islanders have survived on their ability to make every game close, to fight for every puck and to pull out points when they do not have their best.

There was none of that on Wednesday.

The Islanders’ game has been slipping gradually since they finished a homestand by blowing three leads in an overtime loss to the Bruins a little less than two weeks ago.

It suffered a full-on free fall Wednesday night.

There were defensive breakdowns.

There was little to no offensive push for too much of the game.

There were constantly poor breakouts and puck management.

It was, in short, a total capitulation to a team that entered the night in seventh place in the division — closer to last than it was to the Islanders.

On every level, it was a disaster.

“It was pretty ugly,” Brock Nelson said. “For whatever reason, we were the team that wasn’t really ready. Felt a little unorganized, a little lost. Unacceptable, really.”

Rickard Rakell broke through at 6:44 of the second period when he stuffed in Marcus Pettersson’s point shot — a goal initially ruled out on the ice but confirmed on review when it became clear that play hadn’t been blown dead before the puck went in the net. From there, the period became an onslaught.

Jake Guentzel’s deflection from Kris Letang doubled the lead at the 10:15 mark, prompting coach Lane Lambert to use his timeout. That only made things worse.

“What did I emphasize? We had to wake up,” Lambert said. “There was a lot of hockey game left. Clearly it didn’t work this time.”

Right off the faceoff after the timeout, the Islanders let Guentzel stroll unimpeded behind them to make it 3-0 as he finished off a one-on-zero breakaway.

A little over two minutes after that Evgeni Malkin got to the slot uninterrupted to make it 4-0.

By the time the second period ended, the Penguins had scored twice more — first when no one picked up Malkin on the backdoor and he deflected in Letang’s pass and second when Radim Zohorna finished off a breakaway. Letang assisted on five of the six goals in the period — setting an NHL record for assists by a defenseman in a period.

“It’s brutal,” Mat Barzal said. “That’s what it is.”

It was a terrible night for Ilya Sorokin, as he let in six of 25 shots and tied his worst-ever goals allowed mark in a single game, getting pulled after 40 minutes.

Sorokin said afterward he did not remember the last period he played as poorly as the second.

Semyon Varlamov did not get away from the third period clean either, letting in a Valtteri Puustinen goal to make it 7-0 halfway through a final period the Islanders just wanted to end.

Not that either goaltender had any help whatsoever.

The Alexander Romanov-Noah Dobson pair that has done so well in taking up the mantle with Adam Pelech and Ryan Pulock hurt was on for three goals against. Mike Reilly and Sebastian Aho both played turnover-prone hockey and struggled to get the puck up the ice. Samuel Bolduc’s confidence seemed to abandon him. Robert Bortuzzo took a needless penalty early in the game and things never got better.

Coming into Wednesday, the worst loss the Isles had all season was by three goals. They’d been blown out. But not like this.

This was a wake-up call blaring like a siren, taking the form of empty seats and boos.

The Islanders have skated through the season trying to win while the defensive habits that have gotten them success in the past have slowly eroded. It got them as far as second place on Christmas Day, even if that came via a slew of overtime losses.

But not even the injuries they’ve suffered to a trio of defensemen count as a valid excuse for the effort the Islanders turned in on Wednesday.

“We gotta clean up some things,” Barzal said. “As a group, it’s unacceptable for us to give that kind of performance in front of our fans.”