Mohegan — Its spontaneity spoke volumes.

Late in a game near the end of the home team’s second season, Mohegan Sun Arena fans suddenly erupted: “LET’S GO, BLACK WOLVES! LET’S GO, BLACK WOLVES!”

Indoor lacrosse had found a home in Uncasville. At a casino, no less.

Now, nearly two years later, the National Lacrosse League’s New England franchise is set to embark on a fourth season Friday night, its path — and that of the league — tracing a decidedly upward trajectory.

Quite simply, the game’s promoters say, lacrosse’s time has come.

After a big improvement in on-field performance in their second season, the Black Wolves made strides at the box office in their third season last year while qualifying for postseason play a second consecutive time. Average attendance grew to 5,400 fans a game, an increase of more than 2,000 a game over the previous season. Crowds like that represent more than 76 percent of Mohegan Sun Arena’s capacity when it’s configured for lacrosse — slightly more than 7,000 seats.

The team has sold more than 1,000 season tickets for its nine home dates this season, according to Amber Cox, vice president of both the Black Wolves and the Connecticut Sun, the Mohegan Tribe’s Women's National Basketball Association team.

More and more, Cox said, the game sells itself.

“When you start a franchise, you start with the low-hanging fruit,” she said. “We started (marketing to) kids, club teams, the coaches. Now, we’re in the next phase: It’s a great product for sports fans in general.”

Millennial males are definitely on the marketers’ radar. So, too, are families. Most who attend a game return again and again, Cox said.

“It’s an unbelievably exciting sport,” said Mitchell Etess, the former Mohegan Sun executive who’s now an adviser to the tribe. “It’s a better game than regular lacrosse (played outdoors). Faster, more confined. Very fast, a lot of hitting — the perfect game for American society.”

The challenge, Etess said, was getting potential fans to realize that the league’s rosters are filled with the best lacrosse players in the world.

Etess, who had never seen an NLL game before the Mohegans bought a 50-percent share of the league’s then-failing Philadelphia franchise in 2014, said the league has never been in better hands. After years of transiency among franchises, it’s poised for explosive growth, he said.

The league's commissioner, Nick Sakiewicz, a veteran sports executive who played professional soccer after starring at the University of New Haven, arrived less than two years ago.

”The NLL was one of the most underpromoted, undermarketed professional sports leagues I’d ever seen,” Sakiewicz said in a phone interview. Heading into its 32nd uninterrupted season, “It’s extraordinary that it's lasted this long without a plan,” he said.

In late summer, the nine-team league announced it would add two expansion teams next year — a San Diego franchise whose owners are led by Joe Tsai, co-founder of the Alibaba Group, the world’s largest retailer, and the Comcast Spectacor-owned Philadelphia Wings, which will replace the franchise that became the Black Wolves.

League attendance grew by 12 percent last year, with a number of teams “making real money,” Sakiewicz said. “We want to be up to 20 to 30 teams in the next decade.”

The NLL ranks third in average attendance among professional indoor sports, behind the National Hockey League and the National Basketball Association.

Investing heavily in its own digital broadcast network, NLL TV, the league quadrupled the number of games it streamed last year and offered a Twitter Game of the Week broadcast that averaged 344,000 views a game. Just this week, it announced a partnership with CBS Sports Digital to stream live and on-demand games via a subscription service.

Sakiewicz, who planned to attend the Black Wolves’ opener against the league’s defending champion, Georgia Swarm, called Mohegan Sun Arena “a fantastic venue” despite its being “a little on the small side.”

“It’s a great market,” he said, referring to New England. “Not just a lacrosse market but a great sports and entertainment market. We typically play in larger arenas, but Mohegan Sun plays into the sports and entertainment aspect of our marketing. Nearly 60 percent of our fans never touched a (lacrosse) stick.”

Other venues in the league include Buffalo’s First Niagara Center, which seats about 19,000, and Calgary’s Scotiabank Saddledome, which seats more than 19,000. Arenas in Colorado and Toronto seat more than 18,000 apiece. Vancouver’s 6,000-seat venue is the only one smaller than Mohegan Sun Arena.

“It’s a great, intimate venue,” Sakiewicz said of the Black Wolves' home. “Not a bad seat in the house.”

NLL players can attest to the intimacy.

“I don’t know what it is, whether it was the crowd or the energy of the building or the environment. Going to Mohegan Sun, I knew we were in for some trouble,” said David Brock, an NLL veteran who signed as a free agent with the Black Wolves after last season.

“It’s going to get bigger, badder and better,” said Kevin Brown, who chairs the Mohegan Tribal Council and the management board of Mohegan Gaming & Entertainment.

To Brown, the Black Wolves and Mohegan Sun fit like fingers in a glove.

“It’s a combination of cultural and business reasons that we have this team,” he said. “On the business side, we’re looking to provide nongaming amenities and attractions, and that’s something we’re going to continue to do. We already were a Native American tribe that owned a sports team, so adding another one felt right. From a cultural standpoint, what other sport should a Native American tribe be involved in?”

While the Black Wolves have yet to operate in the black, the team’s value is in the traffic it brings to the casino, Brown said. The sport’s growing popularity — participation has grown for 12 consecutive years, and more and more U.S. colleges and high schools are fielding teams — is a sign that profitability may not be far off.

“Ultimately, you’ve got to win,” Etess, the adviser to the tribe, said. “Our goal is to bring a championship here.”

b.hallenbeck@theday.com