Islanders coach Lane Lambert, on Monday, ran one of the most intense practices of the season. On Tuesday morning, he said every game remaining this season will be a must-win for the Islanders, such is their position in the standings. So, although they took home a point Tuesday night for a second straight game, the fact they lost another winnable match is alarming.

This team is far from officially out of it, and with two of their next three games against the Penguins, the Islanders have a golden chance to jump the team they’ve been chasing in the standings. But after Drake Batherson scored the game-winner in a 3-2 shootout loss to the Senators, the Islanders’ third straight defeat and third straight blown lead (all against teams well out of playoff contention), it is hard to be anything other than discouraged about their playoff chances.

“It’s disheartening when you put in an effort and can’t break through,” Lambert said.

All the positivity from Bo Horvat’s arrival is long gone, and until the third period, so was the offensive urgency that he helped bring during his first few games on Long Island.

The Islanders allowed Kevin Mandolese, a goaltender making his NHL debut after giving up six goals to the AHL Cleveland Monsters on Friday, to settle in early. He ended up making 46 saves. That included 18 in the second, 15 in the third and five in overtime as the Islanders started to dominate the puck in the game’s latter half. But it wasn’t enough, and the slow start was an F on the report card.

“I think in the first period, we weren’t quite as crisp as we needed to be,” Anders Lee said. “Led to a little [being] not as clean coming out of our zone, not as clean in some areas. Weren’t getting the looks that we were later in the game and guys were able to get to the net [then].

“[Mondolese] made a lot of saves he didn’t see tonight. He really did. Credit to him for his positioning.”

In overtime, it was déjà vu from their loss Saturday at Montreal. The Islanders again failed to convert at four-on-three, this time following an Ottawa bench minor, and they dominated the entirety of the extra period without scoring. Then in the shootout, Tim Stutzle and Batherson both beat Ilya Sorokin to win the game. Stunningly, not only are the Islanders 0-4 in shootouts, but they have converted just one shootout goal the entire season, and went 0-for-2 on Tuesday.

“Execution wasn’t where it needed to be,” Noah Dobson said. “Couple bouncing pucks, bounced over the stick. Missed the net. Obviously it’s a missed opportunity.”

After Stutzle tied the score with a frozen rope of a wrist shot off the rush at 17:32 of the second period, the Islanders lost the lead on a Brady Tkachuk power-play goal 3:41 into the third. Tkachuk got his stick to Stutzle’s shot at the net and redirected it past Sorokin, who made 32 saves.

Much of Lambert’s harping during that high-intensity practice Monday had to do with boxing out — which the Islanders failed to do on Tkachuk.

Brock Nelson tied it at two for the Islanders on the power play with a one-timer at 7:13 of the third period. In overtime, however the Senators fought right back to take the lead, the game and any morale that was left in the Islanders’ fan base.

The saving grace of this season has been that the Islanders are still playing for something despite having struggled for a little more than two months straight. Their record, truth be told, is not that much better than it was last season at this time — the difference is that the Eastern Conference is much worse, with the Penguins and Capitals both looking exceedingly vulnerable.

“I think, honestly, we do well against tough opponents,” Lee said. “We play extremely hard. Our guys are there and ready, this is a big week coming up.”

Right now, the play of the teams ahead of them (the Capitals lost to the Hurricanes on Tuesday night) is keeping the Islanders in the race far more than their actual play. They can’t rely on that against Pittsburgh, though. And these three losses have hit them like a brick to the head.

After Tuesday, it is on to the next must-win game.