BROOKLYN — My Apple Watch started pinging with “loud environment” warnings right around the time Brittney Griner’s name blared across the PA system.

Elaborate pregame introductions are common in basketball but not usually like this: For Unrivaled’s New York debut last night, the players made a surprise entrance through the crowd. Griner and her Vinyl teammates emerged from the concourse behind Barclays Arena Section 106 and marched down to the court just as the players did recently in Philadelphia. Kelsey Plum, Natasha Cloud and their Phantom teammates did the same a few sections over.

The sellout crowd of 18,261 regularly sent my wrist-worn decibel meter north of 100 during the semifinal twinbill, peaking at 113. (The Phantom beat the Vinyl; the Mist routed the Breeze.) The arena doors only opened at 6pm ET, but a line began forming across the plaza out front by 3pm — not bad for a hastily organized game only a few weeks in the making. Hilary Knight, Sue Bird, Alex Morgan, Kelley O’Hara, Wanda Sykes, Issa Rae, Carmelo Anthony, Jason Sudeikis and Ashton Kutcher were among the celebrities in attendance.

Unrivaled CEO Alex Bazzell explained that his staff had been in advance discussions with Barclays, but with a caveat: “We didn’t expect for it to be this quickly — it was more about next season.”

But the success of the Philadelphia games at the end of January, which drew a women’s basketball regular season record of 21,490 fans, inspired Unrivaled to take a chance and move its semifinals to Brooklyn.

“To be honest with you, it was somewhat of an internal split room on, should we pull the trigger on this? Should we not?” Bazzell said. “Coming off Philly and having that great success was one thing, but we had time to strategize and plan. You had a great partner like Xfinity come in behind it and help amplify it.

“This was all organic. We can look at all the data you want, but ultimately the decision came down to we didn’t play it safe to build this league, so we don’t need to start playing it safe.”

My Apple devices confirmed what my ears heard: it was loud.My Apple device confirmed what my ears heard: it was loud. Joe Lemire/SBJ

Prior to the semis, Bazzell and Commissioner Micky Lawler held a year-end press conference where they shared some key metrics for the on-location games away from their Miami home. The Philly stop generated about $2 million in revenue, including $400,000 in merchandise sales; the full numbers for Brooklyn weren’t immediately available, but Bazzell said it was already profitable.

“My job is to focus on, how do you scale it?” he explained. “Our expectations continue to evolve, but for us, this is less about revenue tonight and it’s more about giving back to the fans that have really shown such great support.”

Where to next?

Lawler called it exciting, reassuring and validating to see a similar turnout in Brooklyn as in Philadelphia. “It’s very obvious to us that the voice economy is very strong in women’s basketball,” she said, “and the fans really carry us as much as the players.”

Unrivaled, since its start, has been a player-driven league, and the fans seemed mostly to cheer for star talent rather than specific teams. The games were set against the backdrop of ongoing CBA negotiations between the WNBA and the union — half the pregame questions to players were about labor issues — and at one point last night, the Barclays crowd loudly chanted “pay the players.”

Unrivaled co-founder Breanna Stewart — who calls Barclays home while starring for the WNBA’s Liberty — said she was “really proud of all the people that put the work in to be able to get to where we are today, specifically in Brooklyn, to have that be a last-minute thing.”

Unrivaled won’t turn into a full barnstorming league. It’s a very different business model to regularly host large-arena contests, plus interest in regular travel — not to mention the cost — is another possible impediment.

But the players were already campaigning for certain cities to be included next year (Houston, Los Angeles, Nashville!), and many fondly reminisced about the energy and spectacle of competing in front of a capacity crowd. In Philly, there wasn’t even a developed WNBA market to support it either.

“It was insane,” Breeze star Paige Bueckers said of that game. “Just the atmosphere and the turnout and the appreciation for women’s basketball. It was record-setting, and you could feel that on the court.”