Matthew Schaefer, with a humble demeanor, simply aimed to secure a spot on the Islanders’ roster after training camp. His modesty, however, belies the expectations that surrounded him.

Adam Pelech, his teammate, had no doubt about Schaefer’s potential. Recalling a summer skate session, Pelech was struck by Schaefer’s exceptional talent. “You could immediately see he was special,” Pelech shared with The Post. “Being a first overall pick speaks volumes, but his performance was incredibly impressive. When people asked if I thought he would make the team, I confidently said, ‘Of course. He’s destined to be one of our top players.’ His talent was evident from the start.”

Pelech’s confidence in Schaefer wasn’t unfounded, but even he underestimated the impact Schaefer would make. Just 27 games into the season, Schaefer has emerged not only as a standout player for the Islanders but as one of the premier defensemen in the entire league.

If anything, Pelech underestimated him.

Through the season’s first 27 games, Schaefer has not merely been one of the Islanders’ best players, but one of the best defensemen in the league, period.

He is rewriting the record books, becoming the face of the Islanders, putting himself into the conversation for a spot on Team Canada and leading the Calder Trophy race. 

Going into the season, the Islanders planned to bring Schaefer along slowly. The idea was to have him on the third pair, maybe on the second power-play unit and let him earn his playing time. 

That all got blown up by the second game of the year, when Schaefer played over 26 minutes against the Capitals, taking over the match.

Within a month he was on both the top pair and the top power-play unit, because anything else would have amounted to a denial of reality.

He’s taking more and more minutes against opposing top lines now, too, and has handled it just as easily as everything else.

“I think the skating alone allows him to be like that, right?” Mat Barzal said last week. “I think you can move like that, a lot of those guys, you look at [Connor] Bedard, his first two years as an 18-, 19-year-old, what held him back, I think, was his skating. This year you see him, I feel like he’s one of the fastest guys in the league now. Sometimes it takes those years of maturing physically to gain speed. But Schaef already has that. That allows him to already be dynamic, to control the ice.”

Barzal, the last Islander to win the Calder, had one of the best rookie seasons in franchise history when he scored 85 points in 2017-18. But he was 20 years old when he did that. Schaefer turned 18 in September.

“I think the similarity that I maybe see, you see him big-eyed in new rinks. You can tell he wants to make his mark early on in the league and show fans in the building how good he is,” Barzal said. “I remember feeling like that in my rookie year. I wanted everyone to know who I am and be dynamic, bring the crowd to their feet. He has that same intensity to want to do that.”

If that is Schaefer’s goal, he’s already succeeded. Almost overnight, he’s become one of the NHL’s most recognizable faces. He does not talk like someone in the eye of a hurricane, though.

“Everything will fall into place if you work hard, you’re a good person and you put the work in,” Schaefer told The Post. “Obviously if you don’t put the work in, you probably won’t have the same outcome. It takes a lot of hard work and dedication. From when I was younger, putting in the time and work, to now, it definitely pays off.”

Patrick Roy, who cut his teeth as a coach in the Quebec Major Junior League, likes to encourage young players to be themselves and take risks, showing faith in them if they make a mistake. Even for highly-touted prospects, the expectation is that there will be at least a few tough moments early.

With Schaefer, though, Roy has often used Nathan MacKinnon — who he coached as a rookie in Colorado — as a point of comparison. Which is to say, there really haven’t been many of those hard moments.

The fact that Schaefer played just 17 games in juniors last season before breaking his collarbone makes it all the more impressive.

“I think it’s good to get those games under your belt and keep working toward the same thing I always live by,” Schaefer said. “I want to get better each and every day, whether it’s off the ice or on the ice.”