Matthew Schaefer is a hit from the blue line to the profit line.

The red-hot New York Islanders are seeing surges in ticket sales, TV viewership and fan engagement — largely thanks to the rookie phenom who wears No. 48.

“We ran out of fours and eights to make jerseys. We hustled to restock,” Kelly Cheeseman, the Isles and UBS Arena’s new president of business operations, told The Post of what fans call the “Schaefer Effect.”

Matthew Schaefer is invigorating Islanders fans to the point that he’s boosting business metrics. NHLI via Getty Images

“It’s real,” he added, also saying overall jersey sales shot up 63% year over year, with the 18-year-old leading the way as the top seller.

Fans love the first overall draft pick for reasons beyond his electric 23 points in 34 games, however.

Fans are going wild for Matthew Schaefer to the point that the Islanders ran out of the red-hot rookie’s jersey numbers. Getty Images

He’s courageously carried on after losing his mother to breast cancer in 2024, and has struck a wholesome chord by living with former player turned special assistant to the general manager, Matt Martin, and his family.

Long Island-adoring Schaefer watches cartoons like “Paw Patrol” with the Martin kids, helps them skate and has his pregame clothes picked out by the patriarch’s wife, Sydney Esiason.

“I think in particular, you’re seeing that vulnerability with Matthew Schaefer,” said Cheeseman, who credits the player for having a role in the team’s 40% boost in social media engagement.

“There’s a lot of things there that are similar and relatable … he’s just a college kid.”

Right back where we started from

On-ice success is also pushing the Islanders ahead from a front office perspective. NHLI via Getty Images

More encouraging metrics, like a 37% rise in broadcast viewership, a 7% increase in ticket sales and a 58% boost in viewers age 25 to 54, don’t just fall on the shoulders of the young defenseman with a heartfelt backstory, Cheeseman said.

The team’s mighty play following a slow start, the 19-12-3 Islanders are second in the Metropolitan division, has been a major driver.

“We have a legitimate chance to sell out every game until the Olympic break,” he said of the February hiatus.

Islanders fans are going nuts for Matthew Schaefer. NHLI via Getty Images

“That’s the trend that I’m more focused on.”

Cheeseman is also striving to grow the fanbase and may be able to poach fair-weather fans in rival Rangers territory amid the Blueshirts’ slumping season.

“It’s about Queens and Brooklyn out to Montauk,” said the biz ops boss, who also wants to make city-based Islanders lovers feel significant.

“I think [the Islanders winning] will ultimately help there, too.”

A plan for the A-List

Reese Witherspoon rooted for the Isles at a recent home game. Instagram/NY Islanders

Cheeseman, who is about 40 days into his role, left the Los Angeles Kings and wants to implement some strategies that worked well in Tinseltown — especially to grow celebrity presence on the island.

“That’s absolutely in the plan … but it needs to be authentic,” Cheeseman said about getting more A-listers in as true supporters rather than a glorified photo op.

Reese Witherspoon made Page Six and had fans swoon in Elmont last Saturday while sporting an Isles varsity jacket and hat during the team’s thrilling 3-2 shootout win over the Tampa Bay Lightning.

“I think Reese is now an authentic fan,” Cheeseman said of Witherspoon, who is dating German financier Oliver Haarmann, a minority owner of the team.

Homegrown Ralph Macchio — he has his own “Karate Kid” Islanders bobblehead — along with Kevin Connolly of “Entourage” and actress Chloe Grace Moretz, are some other devout blue-and-orange faithful.

Celebrity DJ and influencer Xandra Pohl was also sitting on the glass at the team’s home opener.

It takes a village

Kelly Cheeseman, the Islanders and UBS Arena’s new president of business operations, has major plans to grow the team’s base. Sportico via Getty Images

The organization, which saw its social media impressions double, is also appealing to the fashion and lifestyle crowd — the snarkily popular “VIP List” influencers have been in attendance — to grow female fan support, Cheeseman said.

The strategy comes alongside the soft launch of Belmont Park’s extensive, upscale retail village by the arena.

Only about 40% of its luxe stores, including major brands such as Coach, Lacoste, Roberto Cavalli and Swarovski, are open.

The Islanders are building up success to sync with future developments at Belmont Park. NHLI via Getty Images

That gap should be filled by the fall of 2026 — around when the iconic horse racing track, home to the Belmont Stakes, will have been futuristically rebuilt, according to the Islanders.

“That’s what we’re focused on — it will be the real launch to campus,” said Cheeseman, who is also looking ahead to UBS Arena hosting the 2027 NHL All-Star Game.

“We want to connect all that together.”