New York Red Bulls and New York City Football Club players face off in a Hudson Derby. Supporters of the two MLS teams got into a brawl before their final match of the 2015 regular season. USA Today Sports

If you’re looking for some evidence that soccer is beginning to hit it big in the U.S., look no further than the punches thrown Sunday afternoon at Bello’s Pub and Grill, a watering hole in Newark, New Jersey. Bello’s, a longtime gathering spot for fans of Major League Soccer’s New York Red Bulls, was the site of a skirmish between backers of the Red Bulls and supporters of New York City Football Club, or New York City FC, a newly launched MLS expansion team. Before police intervened, the fans threw punches, as well as a sandwich board and some sticks.

Although the Red Bulls technically play in New Jersey and the New York City FC plays in the Bronx, the two teams were scheduled to engage in a “derby,” a term European soccer fans use when teams based in the same city play against one another. It was an event eagerly anticipated by the Garden State Ultras, a longtime fan club that supports the Red Bulls, as well as by fans of the New York City FC.

Nick Chavez, a reporter for Newsday on Long Island, tweeted it’s possible Sunday’s fracas represented retaliation after the Garden State Ultras allegedly attacked and intimidated New York City FC fans outside Yankee Stadium this year.

This is not the first time rival MLS fan bases have mixed things up -- a Portland Timbers fan found himself getting choked with his own scarf by three Seattle Sounders fans after a match back in 2010 -- but the league must secretly be delighted that its teams have roused enough passion and loyalty to start fights in one of the world’s largest media markets. Although it’s grown into a product intriguing enough to export, MLS still has a lot to prove concerning its own domestic popularity.

Neither MLS nor team officials commented on the event Sunday.