The London Spitfire defeated the Philadelphia Fusion in the first round of the Overwatch League Grand Finals on Friday in Brooklyn. (Mike Hume/ The Washington Post)

NEW YORK — The rumble was small at first. Then the man called “Golden Boy” appeared on stage and asked “where Brooklyn at?” and Brooklyn answered with a roar that grew and grew and blended with the BOOM! BOOM! of Biggie Smalls’s bass to make each person in the near-capacity crowd of 11,000 in Barclays Center on Friday night acutely aware of their own heartbeats.

The noise peaked, louder and more powerful than the thunder that blanketed the boroughs from earlier in the afternoon, as the game’s superstars — Carpe (“The fish who will never be caught!”) and Gesture (“The swag kid of London!”) — strutted out, stiffly popping their jerseys. One woman held up a sign requesting Carpe to be his “e-girl.”

“I generally don’t get nervous,” Gesture said. “Rather, because there were a lot of people that showed up today, I was excited to play in front of all of them.”

About two hours later, when the first round of the Overwatch League Grand Finals was over, the arena still buzzed. Gesture had led his squad, the fifth-seeded London Spitfire, to a convincing 3-1 win to take a 1-0 lead over the sixth-seeded Philadelphia Fusion, which had upset former juggernaut New York Excelsior to make the final. London can seal the first OWL title in the second round Saturday, which starts at 4 p.m., but whatever happens, OWL management had already seen what it wanted.

There had been trepidation in scheduling the championship at Barclays Center because all the teams had played the entire season in the 450-seat Blizzard Arena in Burbank, Calif. Could they really sell 20,000-plus tickets over the course of the two-day finals in New York, what one executive called “the capital of the universe?”

The crowd, announced at 11,000, may not have been at capacity with some empty seats in the back of the floor level and in the upper deck, but volume helped bridge the difference. Spray-painted sidewalks alerted the unknowing that the Big Apple was at esports’ epicenter. Fans from Staten Island and California and Canada and South Korea flocked to Barclays. Jerseys in dark blue and light blue and orange and green dotted the streets and subway cars. For a 7 p.m. start, fans lined up at the door starting at 2:30 p.m.

Philadelphia started strong, winning the first game on Dorado, but London’s Fury later chalked that up to “uncharacteristic mistakes.” In the next round, on Oasis, London emerged from large scrums with the upper hand and swept Philadelphia.

“We don’t really call targets … because it’s a really clutch situation,” London’s Profit said. “We just shoot and people die.”

Ryan Courbron, a 19-year-old Boston Uprising fan from Maine, didn’t get to see his team in the finals but he was caught up in the action and seemed not to mind.

The $200 ticket, which he bought right as they were released, was still “well worth it” because at home, he had a small screen. Here, he had fellow fans.

“When you first walk in, you don’t think it’s going to be that big,” said Zach Augustine, a London fan, “but then you [see the stage] and the lights are going, the crowd too. … This is incredible, I’ve never seen so many people who like the stuff I like in one place.”

Jordyn McCoy, a 22-year-old former Texas State student who set up so many watch parties for the Houston Outlaws that the team eventually hired her, cheered and rocked with each long-range snipe and last-second heal.

After halftime, London dominated on Eichenwalde and then grabbed a ho-hum 2-1 victory on Volskaya Industries to close the first round. The night’s defining moment, though, might not have happened on screen. During an intermission, Jeff Kaplan, Overwatch’s game director and lead designer, appeared and received a rock-star-level standing ovation.

Kaplan waved, shook his fists and basked in the glory of creating something that attracted thousands of people to this event. He screamed, “This is awesome!” into the microphone and walked off to a quieter place, where he could watch the rest of the match. The crowd shifted its attention back to the screen and, for one night at least, esports wrested away its fair share of New York City.

Read more from Post Sports

Brewer: Alex Smith was a safe choice. But the Redskins may have lucked into something greater.

Max Scherzer celebrates his birthday by utterly dominating the Marlins

Dwight Howard could provide the pick-me-up in the Wizards’ most used play

This is the man who delivers the most specialized skill in college football

‘My heart, it’s never been fuller’: All black team wins D.C. Little League title