The Islanders and Brooklyn’s Barclays Center both have the ability to opt out of their 25-year license agreement, according to multiple sources familiar with the terms. Despite the existence of the clause, though, there are no indications that either side will opt out.

The Islanders could leave Barclays Center at the conclusion of the fourth year, should either side choose to opt out, the sources said. It is not clear when the sides would have to make a decision about exercising the clause.

The Islanders will wrap up their first regular season in Brooklyn on Sunday night and will begin their first-round playoff series this week against an opponent to be determined after Saturday night’s 4-3 overtime loss to Buffalo.

Brett Yormark, CEO of Brooklyn Sports & Entertainment, which runs Barclays Center, said he has been pleased with the Islanders’ first season in Brooklyn.

“We look forward to a long-term partnership with the Islanders and building on this first year,” he said this week.

The Islanders did not respond to multiple requests for comment. The biggest obstacle they would face if they wanted to opt out is that there isn’t another arena available in the metropolitan area that is seeking an NHL hockey team.

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“I don’t see any alternative right now,” NHL commissioner Gary Bettman said recently. “And that sounds too negative. The fact is, they’re doing well in Barclays and there’s no prospect right this minute of another building on Long Island.”

Experts in sports marketing and business said Nassau Coliseum, the Islanders’ home from 1972 through last season, is not a viable possibility because the renovations would allow for only 13,000 seats for hockey games, which is considered too small for an NHL team. Barclays Center is the second-smallest arena in the NHL with a capacity of 15,795, including about 1,500 obstructed-view seats.

“The fact they want to take [Nassau Coliseum] down in attendance to 13,000, they’re never going to get back a pro team with a capacity that low,” said Joel Evans, a business and marketing professor at Hofstra.

The Coliseum renovations are being handled by Nassau Events Center, which is controlled by Brooklyn Nets owner Mikhail Prokhorov. The project is being managed by Forest City Ratner executive chairman Bruce Ratner, who also developed Barclays Center. Yormark has said he will manage both Barclays Center and the Coliseum after it reopens. Wayne McDonnell, academic chair of New York University’s Tisch Institute for Sports Management, Media and Business, agrees that the Coliseum isn’t suitable for an NHL team.

“It makes more sense for a minor-league team, exhibition games or maybe a handful of special Islanders games to maintain a presence,” McDonnell said.

Nassau Events Center’s contract with Nassau County calls for the Islanders to play two exhibition games and four regular-season games annually at the renovated Coliseum. But Bettman said there are many factors that need to be addressed before the league can sign off on such an unorthodox home schedule. “Since there’s not even a formal request,” Bettman said recently, “I’m not even going to speculate what those factors are.”

Nowhere to go

After more than a decade of failed efforts to build a new Nassau Coliseum, owner Charles Wang announced plans to move the Islanders to Brooklyn. At an October 2012 news conference at Barclays Center, Wang described the 25-year agreement as “ironclad.”

Nearly two years later, in August 2014, Wang agreed to sell a minority stake of the team to investors Jonathan Ledecky and Scott Malkin in a deal that would give them majority control after two years. That transition becomes official this July.

If either side — Barclays Center management or new Islanders ownership — decides to opt out of the Brooklyn deal, the logical metropolitan-area locations where a new Islanders arena could be built have significant obstacles. Ledecky and Malkin were not available for comment.

Queens was touted in 2010 by Mets chief operating officer Jeff Wilpon as a spot for a new Islanders home. There is a convention center but no arena in the Willets Point redevelopment plans, which are held up in court over a state parkland lawsuit. The development company declined to comment.

Nassau officials in 2011 raised the possibility of an Islanders arena on state-owned land at Belmont Park. Empire State Development, New York State’s chief economic development agency, began soliciting bids to develop the land in 2012, but none of the four submitted plans includes an arena. The New York Cosmos, who play in the North American Soccer League, submitted a proposal for a 25,000-seat open-air stadium. ESD has yet to pick a winner, and a spokesman declined to give a timeline for a decision.

“The Islanders shouldn’t have been in the Nassau Coliseum as long as they were,” Bettman said. “People tend to over-romanticize the Nassau Coliseum. They tend to think this is the 1970s, early ’80s. The fact of the matter is, that arena was not a first-class major- league facility and hadn’t been for some time.”

Taking attendance

Bettman said he has been encouraged by the Islanders’ first season in Brooklyn despite the fact that the arena was not built for hockey.

The Islanders’ average attendance through 39 of 41 home games at Barclays was 13,580, which ranks 28th out of the 30 NHL teams. Bettman said he is content with the Islanders’ attendance because it’s similar to what they drew at the Coliseum. The Islanders’ average attendance during their final 10 years at the Coliseum was 13,327.

The Islanders’ attendance at Barclays Center also has been on the rise after a rough first six weeks. Since Nov. 20, they have averaged 14,140 in 28 home games compared to 12,157 during their first 11 games. But even with that uptick, Islanders games have been filled at 86 percent capacity, which experts say is unusual for a team in a new arena. “Whenever there is a new facility or a team in a new city, attendance is always pumped up,” said Evans, the Hofstra business and marketing professor. “You can take any sport you want to take, and the pattern always follows.”

‘Something is missing’

Long Island-based Islanders fans who have gone to Barclays say they are pleased with the modern arena amenities, such as larger concourses, a greater variety of food choices and quicker bathroom lines. But some had complaints about their team’s new home, too.

“In a close game, you sensed sometimes that the Coliseum couldn’t contain the excitement. This place, not quite so much,” said Jennifer Rieger, 32, who is a season-ticket holder from Long Beach. “It’s almost as if something is missing.”

The players hope that during the playoffs, the atmosphere will match that of the Coliseum.

“[Nassau Coliseum] was something special,” John Tavares said. “There’s no secret that that was a pretty amazing experience . . . We obviously hope [Barclays Center] is something similar to that [in the playoffs].”

Bettman acknowledged that he has heard criticism that Barclays Center lacks the same raucous feel as Nassau Coliseum.

“I think the noise factor and the crowd getting into the game has actually increased throughout the season,” he said.

In response to early-season fan complaints, Barclays Center responded quickly. It hired “a hockey-centric entertainment company” to improve the game presentation, and the satisfaction rate of fans who fill out postgame surveys has been on the rise since the first month of the season.

Change at Jamaica

The new commute on the LIRR also is a lightning rod among fans.

Brad Shafran, 40, of East Meadow, said he used to bring his sons — ages 6 and 3 — to most home games at the Coliseum. But he said it’s been a challenge to bring them to Barclays Center because of the train. He said it’s hard to find seats on the connecting train from Jamaica en route to the arena and that the ride home often involves people using language not suitable for kids.

“The commute itself went from going around the corner and a few traffic lights later, you’re at the Coliseum, to a true commute,” Shafran said.

He said he has gone to about 15 games this season compared to almost every home game during the previous three seasons.

Tom Sullivan, 47, of Ronkonkoma, said he went to close to 20 games at the Coliseum last season but didn’t attend his first game at Barclays Center until two weeks ago. He stayed away because of the commute. When he finally went to a game, he said it took him an hour and 45 minutes to get there.

“It felt like I left last night,” he said as he arrived at his seats.

A LIRR spokesman said trains are carrying an additional 4,000 people on game nights, which he said over a course of the season “translates into 320,000 new rides that are generated by hockey alone.” On average, 37 percent of people attending Islanders games come via the LIRR, he said.

‘Hoping they’ll come back’

Former Islanders great Bobby Nystrom, a member of the Stanley Cup-winning teams of the early 1980s, has been impressed with Barclays Center.

“The building itself is absolutely beautiful,” Nystrom said. “It’s too bad it wasn’t designed for hockey. But needless to say, the amenities are very good. The home dressing room is so big, you could almost put the Coliseum in there.”

But Nystrom said it feels strange to see the Islanders anywhere but Nassau Coliseum.

“I hate to say it, but it doesn’t feel like Long Island, and that’s the thing that’s disappointing to me, that we weren’t able to keep the team on Long Island,” Nystrom said. “I’m still hoping they’ll come back.”

Bettman doesn’t think anyone should get their hopes up.

“This is the Islanders’ home,” Bettman said. “That’s what people should be focusing on. If somebody would drop a new arena on Long Island in 20 years, then maybe we would have a discussion. But that’s a silly hypothetical discussion right now.”

With Neil Best