Matt Martin #17 of the Islanders celebrates after scoring against...

Matt Martin #17 of the Islanders celebrates after scoring against the Tampa Bay Lightning during the second period in Game Four of the Stanley Cup Semifinals during the 2021 Stanley Cup Playoffs at Nassau Coliseum on June 19, 2021. Credit: Getty Images/Rich Graessle

Matt Martin was supposed to be a groomsman in Massachusetts. Instead, he was best man at Nassau Coliseum.

First he scored what proved to be the winning goal in Saturday night’s 3-2 victory over the Lightning in Game 4 of a Stanley Cup semifinal. Then he was introduced to another raucous crowd as the No. 1 star for the night, capping an extraordinary personal and professional day.

It was another improbable plot twist to the Islanders’ playoff story, one that has them two victories from their first Stanley Cup Final since 1984.

Martin had been minding his business most of the night doing what he does — hitting people — and the Islanders led 2-0 late in the second period.

Then, at 17:57 of the period, he gathered a rebound and flipped a backhanded shot over the head of goalie Andrei Vasilevskiy to make it 3-0. It turned out to be the deciding goal.

It was the first goal of the playoffs for Martin, and it came while his wife, daughter, parents-in-law, brother-in-law and new sister-in-law were busy at a wedding reception in Massachusetts. Perfect.

Martin’s father-in-law is former NFL quarterback and current WFAN morning host Boomer Esiason, and his wife is Esiason’s daughter, Sydney.

Matt Martin #17 of the Islanders celebrates after scoring against the...

Matt Martin #17 of the Islanders celebrates after scoring against the Tampa Bay Lightning during the second period in Game Four of the Stanley Cup Semifinals during the 2021 Stanley Cup Playoffs at Nassau Coliseum on June 19, 2021. Credit: Getty Images/Rich Graessle

When Esiason’s son, Gunnar, set his wedding date to Darcy Cunningham for June 19, it was with the knowledge that the Stanley Cup Final always is over by then. But that was before the COVID-19 pandemic.

This year’s playoffs will end about a month later than usual. Oops.

Martin said the personal circumstances of Saturday night "absolutely" added another layer of coolness to his performance.

"It was my mom’s birthday the 17th and Father’s Day tomorrow and Gunnar and Darcy’s wedding today," he said. "I told my mom I was going to get her a goal the other night [in Game 3] and didn’t, so I was able to get her an assist and she was happy with that.

"Honestly, very happy for Gunnar and Darcy. They’re a hockey family, the Esiasons, and they’re having a great time watching us play, and obviously very happy for the position that we’re in and obviously know that I’ve been chasing this for a long time.

"So my heart obviously is with them but here as well, and happy we were able to get a win tonight."

Martin, 32, is exceptionally close to Gunnar, 30, who has waged a public battle with cystic fibrosis since he was a toddler.

"One of the greatest things that’s ever happened to Gunnar is that his sister married Matt," Esiason told Newsday last week. "Matt has been the kindest, greatest friend that Gunnar could ever ask for."

He added, "Matt’s impact on Gunnar has been immeasurable. When Sydney and Matt were dating and Gunnar was at home and really sick, Matt would be over and hang out with Gunnar and they would do their video game thing. He became like a big brother to Gunnar."

Esiason said Matt, Sydney, Gunnar and Darcy all are close with one another.

Sydney posted a video on Twitter of her dancing at the reception with a cardboard cutout of Martin in his Islanders uniform. Usually a fixture among the Islanders’ wives and girlfriends at the Coliseum, she missed Games 3 and 4 for the wedding, but now there is guaranteed to be at least one more game at the Coliseum for her to attend.

The Martin goal survived a coach’s challenge by the Lightning, who asserted the Islanders had been offside earlier in the sequence.The goal was confirmed, and Martin got to continue his unexpected wedding night role as hockey toastmaster.

The Esiason/Martin family drama was another sign of something special going on with these Islanders. Same with the way the game ended, as defenseman Ryan Pulock made a save on Tampa Bay’s Ryan McDonagh in the waning seconds to keep the puck out of an open net.

There was the usual rough stuff along the way, as always led by Martin and linemates Cal Clutterbuck and Casey Cizikas.

After the Lightning scored twice in the third to put a scare into the crowd, Martin knocked Erik Cernak out of the game with a devastating check and fans began chanting Martin’s name — a displaced member of the wedding party who found another party rocking in Uniondale.

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