Mathew Barzal skated out under the bright Nassau Coliseum lights with his helmet off, pumping his fist and repeatedly screaming “our house” to a raucous crowd of 12,000 strong, while his name was announced as the first star of the night.

The 23-year-old Barzal not only swatted home the game-winning goal in the Islanders’ 4-1 victory over the Bruins on Saturday night, but he also maintained the lengthy puck possession that led to the crucial game-tying tally.

Casey Cizikas and Jean-Gabriel Pageau both potted empty-netters for good measure late in the third period as the Islanders knotted the second-round playoff series at two games apiece.

Without Barzal’s heroics, the Islanders would be in a much different situation as they travel to Boston for Game 5 at 6:30 p.m. Monday.

Barzal, who batted a bouncing puck in at 13:03 of the third to give the Islanders a 2-1 lead, just scored his first goal of the postseason in Game 3 on Thursday. Despite Barzal’s struggles early in the playoffs to get on the score sheet, Islanders head coach Barry Trotz said the top-line center was focused on being effective away from the puck and that the points would come soon enough.

Indeed, they have. And just in the nick of time.

“Honestly, it’s the playoffs,” Barzal said after his second two-point night of the postseason. “As much as I’d love to produce every night, just it’s so tight out there, and sometimes it just doesn’t come that easy. It’s more so, when it’s not coming offensively that night, just make sure I’m not on the ice for any goals against or making that block or just trying to get the puck out. Just playing sound hockey, a lot of shifts are just 50-50, and you just got to grind it out.

“So when things aren’t going my way in the playoffs offensively, that’s really what it comes down to, just battling for the boys.”

The Islanders were down 1-0 early in the second period, after the Bruins had capitalized on the power play with a goal from David Krejci. Barzal fended off Boston fourth-liner Curtis Lazar with some sharp skating along the boards before dishing to Kyle Palmieri for the shot in front to tie it up 1-1 at 6:38.

It’s hard to ignore that Barzal and Palmieri have generated two goals together in the past two games, with Palmieri on the top line for a shift in place of Leo Komarov, who both times was taking a breather on the bench after a penalty kill.

Asked if he is tempted to put Palmieri in place of Komarov on the top line with Barzal and Jordan Eberle, Trotz said prior to the game that it had been considered. Trotz buckled down, however, on his lineup decisions after the win.

“I think Palms is pretty valuable for that line that Pageau is on, that line produces for us,” he said. “You can play fantasy hockey all you want, Leo’s good with Barzy and when I put Palms there they’ve been good. But both times, it’s been after power plays or just happenstance when guys have issues with equipment or get marked up a little bit.”

Trotz added that he felt the penalty kill gave the Islanders some momentum to build off. When Krejci scored through a scramble in front of Islanders goalie Semyon Varlamov at 3:57 of the second, Trotz challenged for goaltender interference. The goal was upheld and the Islanders were sent right back on the penalty kill.

“We had a huge penalty kill on that challenge, and then [Barzal’s] line came out right after that and they were pretty determined,” Trotz said. “I thought that penalty kill gave us a bit of a boost, and then obviously when we scored right away that really got us going in the right direction.“I liked Mat’s game, he was dangerous all night and he kept putting the puck to the net and creating. That’s how you’re going to score in the playoffs, and he’s doing it right now.”