Matthew Schaefer exudes an unshakable calmness.

At just 18, this hockey prodigy is making waves with the New York Islanders, effortlessly excelling both on and off the ice during his first month in the NHL on Long Island.

“I had only visited New York City once a couple of years back, so Long Island was pretty much a mystery to me,” the promising NHL newcomer shared with The Post after a recent practice session.

“Now, it feels like I’ve known this place my whole life,” remarked the Ontario native, who recently broke Bobby Orr’s longstanding record, becoming the youngest defenseman to achieve a multipoint game.

Schaefer has quickly become beloved by fans sporting the blue and orange, earning respect for his remarkable emotional resilience following the loss of his mother, Jennifer, to breast cancer earlier in 2024.

“She would just light up a room — her smile, her laugh, she was always joking around,” he said at the start of the NHL’s Hockey Fights Cancer month. “She was always having a great time and always happy no matter what she was going through.

“Every night, I always talk to her,” said Schaefer, whose jersey on draft night had his mom’s initials and breast-cancer awareness ribbon stitched on.

The promising talent also said he’s looking into getting involved locally for cancer causes.

“I just wish she were here and I was able to give her a hug.”

Extended family

Schaefer is surrounded by support on LI, living with beloved former Islander Matt Martin along with his wife, Sydney Esiason Martin, and their children — rather than an isolated hotel room or empty apartment.

“We’re doing lots of things together — video games, all that stuff,” he said of Martin, who is a special assistant to general manager Mathieu Darche.

“I guess I’m not really a fighter, so maybe he can make me a little tougher,” Schaefer quipped of Martin.

Schaefer said he makes time to watch “Paw Patrol” with the Martin kids — and they return the favor by rooting him on in front of their TV.

He’s also borrowing some stylish items from Martin’s closet to the point that it’s now a household norm.

“The pregame routine is, when I get up from my nap, I text his wife, and I go, ‘I’m ready.’ And she has an outfit ready for me — and it’s just all his clothes.

“I guess I don’t have to worry about looking good when I come to the rink,” he said jokingly.

The new ritual also evokes something very special that Schaefer used to share with his mother.

“My mom would always dress me and dress me up — whether it’s pea coats, turtlenecks and all that,” he said.

“She definitely got some style into me, and then now, obviously, I’m getting even more style into me.”

It’s not just Schaefer’s compelling backstory that wins over the stands, though. UBS Arena erupted during the team’s home opener against Washington when No. 48 scored his first-ever NHL goal — and many times since, for Schaefer’s mighty play.

“I love these guys — all of the fans, everything,” he said of the “passionate” bunch that’s gushing over him more each game.

“And we don’t like the Rangers.”

Ragging on the ‘Rags’

Schaefer teased Blueshirts great-turned-broadcaster Henrik Lundqvist during a Wednesday interview with TNT, to the joy of many Isles fanatics.

“It’s pretty tough to get a Ranger asking the first question,” Schaefer said — as LI native and co-host Liam McHugh was waiting his turn to chime in.

When former NFL great and East Islip native Boomer Esiason — the dad of Martin’s wife — jokingly wore a Rangers jersey for Halloween, Schaefer covered the logo with his hands.

He’s also particularly fond of the Islanders fans’ traditional singing of, “If you know the Rangers suck, clap your hands” to the tune of “If you’re happy and you know it.”

Schaefer said it reminds him of a razz that loyalists of his former Canadian Hockey League team, the Erie Otters, chant about the rival London Knights in Canada.

“We made fun of London, now we’re kind of doing the same thing here for the Rangers. I mean, it’s pretty cool,” he said ahead of the Isles’ Saturday night 5-0 steamroll at Madison Square Garden.

“I love it.”

Eating it up

If the teen has ruffled any Long Island feathers, it occurred benignly in September when he disclosed a controversial bacon, egg, and cheese bagel order that contained “guacamole.”

The young player said he remorsefully misspoke and actually ordered just avocado.

“I don’t know why I said guacamole,” he said.

Schaefer is actually diving into the Long Island food scene with enthusiasm and has been exploring several Manhasset restaurants and various steakhouses.

The local cuisine has won him over enough that, should his girlfriend, Samantha, come down from Prince Edward Island, Schaefer said, “I don’t think we’d go into the city” for date night.

“Maybe [after] go to the beaches, maybe go for a walk or something like that, get some fresh air,” he said.

“We’re not too picky.”

Schaefer is also looking forward to golfing at Long Island’s bounty of courses and exploring areas such as the Hamptons, where he went with teammates to play Sebonack.

“I’m very inconsistent. I don’t get out enough to be really good. So honestly, I’d have to say, [I shoot] like, high 90s on a really good day, and then, mid-hundreds on a bad day,” he admitted of his golf swing.

“I mean, if my driver’s good, then I think that helps,” added Schaefer, who went to the Ryder Cup to watch.

Beyond the glamorous life of a new NHL star, Schaefer said his mind remains focused on two things — hard work and gratitude for unwavering family support.

“I don’t think I would get here today if it weren’t for my family,” Schaefer said of his dad, Todd, brother Johnny, and his late mom, Jennifer.

“I know she’s always with us in spirit. … I know she has a front-row seat.”