PITTSBURGH — The Islanders’ playoff hopes took a disastrous blow on Monday morning with the news that Mathew Barzal is week-to-week with a lower-body injury.

With just 22 games left for the Islanders, and six teams separated by three points in the wild-card standings entering Monday, being without Barzal for any period of time — let alone a potentially extended absence — is an utter calamity. The Islanders were already dealing with injuries to Jean-Gabriel Pageau and Josh Bailey, both of whom missed the trip to Boston and Pittsburgh. Adding Barzal, their most dynamic offensive player, to the mix was the last thing the Islanders could afford.

“Barzy’s a dynamic player, one that can change the projection of a game pretty quickly,” Isles captain Anders Lee said. “The way he handles the puck and possesses it, it’s a huge factor in our team’s success. Having him out, it’s a big loss for right now in the interim and we’ve gotta find a way to fill those shoes.”

That will be easier said than done. Barzal’s 51 points are second only to Brock Nelson on the team and he had been rapidly developing a 1-2 punch with the newly acquired Bo Horvat on the top line. Barzal is also a staple of the top power-play unit and can eat up minutes reliably.

In the four games he played before getting hurt, Barzal averaged 22:26, including a season-high 25:50 in a shootout loss to the Senators last week. The plan to get into the playoffs was very much predicated on riding the top line and hoping Barzal and Horvat could make up for the scoring issues the Isles had throughout January.

Suffice to say, that plan is up in smoke after a seemingly innocuous hit from Craig Smith knocked Barzal out of Saturday’s 6-2 loss to the Bruins just 6:01 into the match. Barzal went back on the ice during a TV timeout to test things out, then spent the rest of the game in the locker room.

The one good piece of news for the Islanders is that they are planning to have Barzal back before the end of this season. That comes as a relief, particularly after coach Lane Lambert refused to clarify not only Barzal’s status for the rest of the season, but for as far out as next season’s training camp at Monday’s morning skate.

Still, the timing could not be worse for the Islanders, who played a pivotal game on Monday against the Penguins and need to start stringing together victories to avoid another disappointing playoff miss.

“I don’t think there’s a good time for somebody to get hurt, but this definitely isn’t one of those times,” Horvat said. “Obviously he’s a huge part of this team and a huge part of this offense and stuff like that. So obviously he’s gonna be missed but like I said, we can’t have any excuses for ourselves. Just gotta go out there and play.”

Simon Holmstrom took Barzal’s place next to Horvat on the first line on Monday, and Arnaud Durandeau made his NHL debut on the third line with Casey Cizikas and Hudson Fasching.

Much as the Islanders would like to lean on the cliche of next man up, it is quite hard to see how Barzal is replaceable within this lineup.

“He’s gone through this stuff, he’s gonna be back just fine,” Lee, who dealt with an ACL tear that kept him out of the 2021 playoffs, said. “It’s one of those things that takes a little bit of time and he’s gonna be coming back stronger than ever. That’s how these things work.

“It’s an unfortunate circumstance to go down with an injury, but you learn a lot about little things, what you need to do to get back. Barzy’s got a work ethic that’s gonna get him back sooner rather than later.”