Islanders' Matthew Schaefer scores in overtime to beat Maple Leafs after feeling under the weather all day

The game clock stayed frozen, showing 48.1 seconds left, as the Islanders started their celebration. Of course it did. It was just emphasizing the impact Matthew Schaefer had on the outcome.

“He is a difference-maker,” Emil Heineman said. “He brings us back in the game. Both goals are huge.”

No. 48 converted Mathew Barzal’s brilliant wraparound backhand feed to the slot at 4:11 for the second overtime winner of his rookie season as the Islanders beat the Maple Leafs, 4-3, on Saturday night at sold-out UBS Arena.

Heineman tied the score at 3-3 when he got open in the right circle at 17:15 of the third period.

Schaefer, 18, who felt under the weather all day and uncharacteristically opted not to participate in the team’s optional morning skate, tied the score at 2-2 at 11:10 of the third period with a lightning-quick rush around defenseman Morgan Rielly to finish at the net.

“You just got to go out there and play as hard as you can,” Schaefer said. “I know my [late] mom gave me a little bit of strength throughout the game to just keep going.”

Nicholas Robertson regained a 3-2 lead for the Maple Leafs 62 seconds after Schaefer’s highlight-reel rush.

“[Schaefer] put on a heck of a show in that third period,” Patrick Roy said. “He’s a game-changer. I was happy with the way we played in the third period. Because in the second, I wasn’t pleased. I saw a few things like one-on-three trying to beat their guys in between legs.”

The Islanders (23-15-4), rebounding from Thursday’s brutal 7-2 loss to the visiting Mammoth, scored more than two goals for the first time in nine games. David Rittich, in his seventh straight start, made 18 saves.

Auston Matthews scored twice in the second period for the Maple Leafs (19-15-7) after Islanders defenseman Adam Pelech opened the scoring at 1:10 of the middle frame. Matthews moved past Mats Sundin and set a franchise record with 421 goals.

John Tavares was Schaefer 17 seasons ago, just a kid from the GTA (greater Toronto area) selected first overall by the Islanders and making an immediate impact in the NHL.

They faced each other for the first time on Saturday night with Tavares now in his eighth season with his hometown Maple Leafs and on his second contract with Toronto. Before the game, he said he had yet to meet Schaefer but understood why they were linked.

“Coming into the Islanders as a No. 1 pick and him as well, it’s easy to relate that,” said Tavares, 35, who had 272 goals and 349 assists in nine seasons with the Islanders. “For me, throughout the course of my career, you always think about the journey and where things started and how you got there and where you’re at today. You think about it all the time, the excitement, all the work to get drafted, to earn an opportunity in the NHL and have the expectations that I had.”

Tavares had 24 goals and 30 assists in 2009-10, his rookie year. “Just how much fun it is to go through it for the first time and certainly the ups and downs,’’ he said. “There was a lot of them for me throughout my first year. It’s something I’m very grateful for, very fond of and will never forget.”

It marked only the second instance of two players drafted first overall by the Islanders facing each other in an NHL game.

Billy Harris (also from Toronto) became the Islanders’ first-ever pick when he was selected No. 1 overall in 1972 before being included in the deal that brought Butch Goring to Long Island from the Kings on March 10, 1980. The teams met in the playoffs that season. Harris first played in the regular season against his former team and Hall of Famer Denis Potvin, selected first overall by the Islanders in 1973, on Nov. 1, 1980.

Unlike Tavares, from Mississauga, Ontario, Schaefer did not necessarily grow up in Hamilton, Ontario, as a rabid Maple Leafs fan, though his brother Johnny did. He was more interested in participating in sports than watching.

Schaefer has 12 goals and 16 assists in 42 games and leads the Islanders with an average ice time of 23:50.

He became the youngest defenseman in NHL history to score 10 goals with a power-play tally on Thursday. He became the youngest defenseman in league history to reach 25 points in Tuesday’s 3-2 shootout win in Chicago. On Nov. 14 in Utah, Schaefer became the youngest player in NHL history to score in overtime. And on Nov. 2 against Columbus, he became the youngest defenseman to have a multigoal game. Now he’s done it twice.

“He’s obviously a stud,” Tavares said. “The way he can play the game has been really special.”

Notes & quotes: Defenseman Cole McWard, 24, logged 14:50 in his Islanders debut after being recalled from AHL Bridgeport. He was paired with fellow righthander Scott Mayfield, who moved to his off-side. Both are from St. Louis .  .  . Goalie Ilya Sorokin (lower body) was activated off injured reserve and backed up Rittich. Sorokin is expected to start on Tuesday against the visiting Devils .  .  . Bo Horvat (lower body), injured Thursday, skated on his own.

By Andrew Gross

andrew.gross@newsday.comAGrossNewsday

Andrew Gross joined Newsday in 2018 to cover the Islanders. He began reporting on the NHL in 2003 and has previously covered the Rangers and Devils. Other assignments have included the Jets, St. John’s and MLB.