BUFFALO — All of a week ago, the Islanders spent a few hours atop the Eastern Conference.

Now they are limping toward the NHL’s holiday break, and after Saturday had to watch other results to see whether they would remain above the playoff cutline.

Aside from the variations of a tight standings picture before Christmas, which can flip one way or the other quickly, the Islanders did look better on Saturday than Friday, but not enough to complete a comeback win over the Sabres.

Instead, Emil Heineman’s game-tying goal with under 30 seconds left in regulation left the Islanders with a mere point as they lost 3-2 to Buffalo in a shootout on Josh Norris’ winner.

“Not satisfied with that,” Ryan Pulock, who had called this the most important game of the season, told The Post. “But I think considering where we were at in the game, obviously getting that game to overtime was great. … You don’t want to put ourselves in that position. We gotta be better in that aspect. Finding a way to come back was important.”

This has been the first time all year that, for extended periods of time, the Islanders have lapsed into looking old and slow.

There were moments later in the game where simplifying things worked well, helping them to come back, but it was far from the consistent performance they were looking for.

Not only have the breakouts been poor, but the neutral-zone stinginess on the defensive side fell apart for long stretches on Saturday.

Again and again, the Sabres got behind defensemen, with Pulock in particular getting caught multiple times.

Even with that, the Islanders came into the third period with a chance to erase a two-goal deficit after Mathew Barzal lifted his own rebound past Alex Lyon to make it 2-1 with 23 seconds to go in the second period.

The third-period push they needed didn’t materialize until late, with a pair of penalties in the period’s first 10 minutes handicapping the Islanders’ ability to generate anything offensively.

With 1:27 to go, they were handed a golden opportunity when Michael Kesselring slashed Anders Lee’s stick, allowing the Islanders to skate the rest of regulation at six-on-four. Heineman’s one-timer from Barzal’s cross-crease feed was the look the Islanders needed, and the Swede tied the game at two.

“It didn’t go our way again early in the game, but we stuck with it and dug in, found ourselves clawing back in that game and getting that big point,” Lee said. “… For us to stick with it and find a way to get a point here, obviously wanted two, but that was a big one.”

Lyon was a standout performer in overtime, where the Islanders had the bulk of the looks, and bested David Rittich in the skills competition.

The Islanders’ netminder finished with 30 saves, but was upset afterward over Tage Thompson’s second-period goal, saying the puck never went in the net.

Thompson had appeared to tuck the puck in behind Rittich at the post, and it was called a goal on the ice, but with the puck underneath the goalie, there was no conclusive angle for the Islanders to challenge.

“Seventy-five cameras at the stadium and not even one showed the puck in the net,” Rittich said. “The only guy who saw it was the ref.”

Rasmus Dahlin scored on the power play just 1:47 into the game, cutting through Jean-Gabriel Pageau, Heineman and Pulock before finishing beautifully on his backhand, with Lyon picking up the primary assist.

For much of the early goings, the Islanders looked disorganized and disconnected, struggling to get through the neutral zone and to stop Buffalo from doing the same.

The Islanders can hang their hats on their resilience. But they’ll need to start finding the rest of their game — and soon.