BUFFALO — If Friday night represented some of the best the NHL regular season can offer, then it’s a good thing college football dominates the ratings on Saturdays.

As for the people who did tune into Islanders-Sabres, they were treated to the first regulation loss of the season for the Islanders, 3-1, and a mess of one at that.

Playing on a back-to-back for the first time all season, the Islanders played low-energy and low-intensity hockey — never establishing a forecheck and rarely getting the puck deep.

They were thoroughly outshot, spared from worse only by a strong night in goal from Semyon Varlamov, and for a second straight night repeatedly took bad penalties.

“I just think we got outplayed,” Kyle Palmieri said. “And the final result was what it deserved to be. Varly played a great game, he made some big stops, kept us close and kept us in it. But probably didn’t deserve to be in that one.”

It took the Sabres until 16:37 into the second period to solve Varlamov, when Jeff Skinner’s right-circle one-timer beat the goalie following Casey Mittelstadt’s feed from the crease, but that goal was a long time coming and once the dam opened, the Islanders couldn’t close it.

The Islanders recorded just 25 shots — failing to break double digits in any of the three periods — despite getting four chances on the power play. They made sloppy mistakes the night before against New Jersey, but the lack of oomph in their game made Saturday night worse.

“I thought whether it was intensity or whatever it was, they won a few more puck battles than we did,” coach Lane Lambert said. “As a result, we ended up in our zone and then fatigue sets in. And fatigue sets in when you are playing a back-to-back.”

Mattias Samuelsson extended the Buffalo lead to 2-0 less than three minutes after Skinner’s opener, beating Varlamov from the slot after a loose puck squirted his way.

Less than three minutes into the third, Dylan Cozens put a bow on it, finishing Rasmus Dahlin’s pass across the crease after the defenseman skated in unimpeded, rendering Noah Dobson’s goal with 1:21 to go a mere consolation prize.

A week after walking out of UBS Arena with a feel-good opening night win over these very same Sabres, the Islanders got on a flight home with some real questions to answer for the first time this season.

Inserting Oliver Wahlstrom into the lineup to play on the first line did not yield much — Wahlstrom, still not quite himself after offseason knee surgery, is still feeling his way into things.

Julien Gauthier, who made his Islanders debut on the third line in place of Hudson Fasching, wasn’t much of a factor either.

Varlamov, at least, looked sharp in nets, stopping 40 of 43 shots. For the second straight night, however, good goaltending was not enough — and this time, it wasn’t even close to enough.

“We weren’t as crisp as we needed to be,” captain Anders Lee said. “Our detail wasn’t what it needed to be on a back-to-back, it has to be better. And then on top of that a little bit of execution. Puck wasn’t settling for us enough, we were making mistakes and they were coming right back at us.”

Asked what was behind their issues, Palmieri replied, “Everything.”

“Execution, coming out of our zone, finding ways to get it up the ice and into their zone and sustain some pressure,” he said. “There really was none.”

One bad game does not erase three mostly good ones, and every team will put up a few terrible performances over 82 games.

But for the first time in this young season, the Islanders have some adversity on their hands.