It looks like the city has a new team to root for. And no, it’s not the Brooklyn Nets.

Last weekend on Randall’s Island, the New York Empire wrapped up a three-game sweep of the Philadelphia Phoenix in a heated ultimate frisbee match. But this wasn’t any sort of do-it-yourself pick-up game. The stakes were higher than that.

The Empire is one of the newest additions to the nascent American Ultimate Disc League (so named to avoid copyright infringement on the word “Frisbee,” a registered trademark of the Wham-O toy company), and the team was defending its No. 2 spot in the Eastern division.

With a score of 23-22, the Empire maintained a healthy lead until the very end, when the Phoenix, who are in third, came dangerously close to tying it up in the remaining few seconds of the game with a last-ditch hail mary into the end zone that went uncaught.

If you furrow your brow at the thought of professional frisbee playing, you have reason to do so. The game, invented in the 1960s, is not historically as competitive as other American sports like baseball and football. It has a reputation tied to hippiedom. There are no refs at the club and college level, either, and players prize its self-officiated nature, which is related to the “Spirit of the Game,” a set of values that dictate how the sport is supposed to be played: with integrity and fairness, above all else.

But according to AUDL commissioner Steve Gordon, the culture of the game is becoming much more athletic. “It’s comparable to soccer in terms of cardiovascular requirements,” he told the Transom.

As it turns out, nearly 5 million people in the United States played ultimate frisbee in 2011 alone, according to a report by the Sporting Good Manufacturers Association, which monitors such numbers. (That’s more than rugby and lacrosse combined.) So the goal of the AUDL, which was formed last year, is to tap into that growing base.

The league is one of two in the country (the other, Major League Ultimate, branched off from the AUDL in 2012 and had its first season this year), and it’s composed of 12 teams, divided into two conferences, with 16-game seasons of about four months.

Empire general manager Cullen Shaw said that the league would like to grow to 32 teams eventually (the Toronto Rush, undefeated, are currently in first place). And, he noted, players mainly commit to the league out of pure passion; there’s really no financial incentive.

“These guys aren’t making much out of this,” Mr. Shaw said. “They do it because they love it, and this is a chance to represent their city.”

“We’d like to play there next year,” he added, pointing to the neighboring Icahn Stadium on Randall’s Island, which towers over the team’s current home field.

For now, however, it’s a bit of a shoestring operation. Attendance at Saturday’s game was relatively scant—only about 60 fans showed, by the Transom’s count, and they appeared mostly to be friends and family members of the players. There was no scoreboard, one fan pointed out with disappointment, because the league didn’t pay for a generator to power it. The refs, it often seemed, were unsure of their calls.

Still, the spectators are a devoted bunch. They take this game about as seriously as the players do. One lonely but impassioned Philadelphia fan was heckling the opposing team the entire game, blowing raspberries into a red vuvuzela, which matched his team’s color.

And while it may take a while for professional ultimate to catch on—and for the league to work out all its kinks—Mr. Gordon, Mr. Shaw and everyone else the Transom talked to believe that ultimate will, ultimately, get the respect it deserves.

As one Empire fan wisely put it: “Growing pains, we’ve all got ’em.”

Photos by Fernando Gomes