Islanders goaltender Ilya Sorokin and Adam Pelech look on as...

Islanders goaltender Ilya Sorokin and Adam Pelech look on as the Senators' Brady Tkachuk scores while under pressure from Simon Holmstrom during the third period on Thursday in Ottawa. Credit: AP/Adrian Wyld

 OTTAWA, Ontario — It’s imperative to play playoff-like hockey to qualify for the playoffs.

The Islanders fell short on Thursday night in a 3-2, last-second loss to the Senators at Canadian Tire Centre, which is why they now are out of a playoff spot for the first time since Dec. 4.

“We’ve got a lot of big games coming up down the stretch,” Mathew Barzal told Newsday. “If we just take care of our games, I’m sure we’ll be all right.”

Saturday’s game against the Canadiens to conclude this three-game Canadian swing and Sunday’s home game against the Blue Jackets now are must-win situations.

Playoff hockey means stingy hockey, and there was plenty of that on Thursday. It means physical hockey, and Anders Lee and the Senators’ Brady Tkachuk fighting off the opening faceoff, Brayden Schenn dropping the gloves with Ridly Greig at 5:54 of the first period and Dylan Cozens roughing up Matthew Schaefer a minute later showed there was an intensity to the game.

But it also means getting stronger as the game progresses, not fading in the third period. That’s what did in the Islanders (39-25-5).

They simply can’t be outshot 11-1 in the final 20 minutes, even if the one shot produced Schenn’s go-ahead goal at 2:02 of the third period. The Islanders simply can’t turn the puck over as much as they did or repeatedly get beaten to the puck and on puck battles to the point that breaking out of their own zone seemed a foreign concept.

And they can’t go 0-for-4 on the power play with only four man-advantage shots on a night when Franklin Square’s Shane Pinto scored shorthanded in the second period to tie it at 1-1.

Whenever the Islanders had a chance to seize momentum, it instead swung toward the Senators.

“I liked our first 40 minutes,” coach Patrick Roy said. “I really thought we had some good looks. We had some good chances in that second period.

“[In the third period], for some reason, they did a better job than us to be on those 50-50 pucks. We made a few turnovers. That gave them some momentum and we had a hard time getting out of the zone. It’s a team that put a lot of pressure on the forecheck and they did a good job against us in that regard.”

Roy continued by saying the Islanders’ on-ice communication was better in the first and second periods, as was their poise with the puck.

Again, being able to play playoff-like hockey would dictate that remains constant, if not improved, during the final 20 minutes.

Particularly given that the Senators theoretically were the more tired of the two squads. They lost in Washington on Wednesday night and arrived home early in the morning.

That the Senators had more energy and, yes, hunger at the end should be concerning, if not downright alarming.

“This time of the year, there’s not much room out there,” Schenn said. “It’s stingy. You’ve got to check for your chances and you have to play on defense. The third period, I don’t know if we sat back or they came at us, but they caught a bounce at the end.”

Tkachuk stuffed in the puck off a scramble around the Islanders’ crease with 13 seconds left in regulation.

To be fair, if Ilya Sorokin (23 saves) had not somehow stretched out his arm to get a piece of Michael Amadio’s two-on-one blast at 16:10 of the third period before the puck glanced off the post, the Islanders’ fate might have been sealed earlier.

Either way, not getting at least one point cost the Islanders their spot among the Eastern Conference’s top eight.

The Bruins and Red Wings both won to maintain wild-card spots and the Blue Jackets beat the Rangers to move past the Islanders into third place in the Metropolitan Division.

It was just that type of night for the Islanders. Sometimes everything goes awry.

“Too many times in that third, we were just trying to get it out of the zone,” Lee said. “And then you’ve got to change and they’re coming back at you. We didn’t break that enough.”

Lee readily accepted Tkachuk’s request to fight right at the start of the game. Tkachuk clearly wanted to make a statement after the Senators’ loss, but Lee felt he could do the same for his team.

“I said, ‘Let’s do it,’ ” he said. “It was great. I was all for it. A big game for both of our teams. Let’s start it off with a bang.”

That works only if the game doesn’t end with a whimper.

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