A sellout crowd filled Nassau Coliseum to see the suddenly resurgent Islanders — who were on a two-game win streak thanks to triumphs over the hated Rangers and rival Devils — and wunderkind John Tavares, the freshly-named NHL’s First Star of the Week.

It’s a shame the Islanders had to ruin all the positive vibes on Presidents’ Day with an effort — by far their worst of the lockout-shortened season — that reminded everyone why expectations were so low to begin with.

They fell behind just 26 seconds into the contest, and the afternoon only grew unbearably worse in a jarring 7-0 loss to the middling Flyers — the worst home shellacking in Islanders history.

“To play like that is just unacceptable,” Tavares said. “We can’t have efforts like that.”

If it were a boxing match, the fight would have been stopped in the second period, and saved the Islanders’ faithful their vocal cords.

They spent large portions of the rout groaning and booing. There was even a brief “DP” chant for beleaguered backup goaltender Rick DiPietro after Evgeni Nabokov, left out on an island much of the afternoon, was beaten for the third of what would be seven times.

“He’s been playing great for us,” defenseman Mark Streit said of Nabokov. “We just didn’t help him enough and they scored way too many goals.”