There’s a riveting sideshow that happens on the courts of the Billie Jean King National Tennis Center during the US Open in Queens each year — and it has nothing to do with the famous players vying for the crown.

The event’s quick-footed and eager “Ball Crew” regularly enthrall the crowds as they zip across the facility’s famous blue arenas between every serve and volley to scoop up balls discarded by the likes of Naomi Osaka and Carlos Alcaraz.

There are 315 members of the agile work crew, and they range in age from 14 to their early 50s, according to team leader Neal Kitson.

Each person is put through a rigorous try-out that tests their agility and speed for grabbing balls off the court in the middle of game play.

This year, there were only 80 spots for newbies open. Out of 1,600 applicants, just 500 were invited to try out — and 420 were sent home.

At 14 years old, Jayden Wong is among the youngest ball kids serving the iconic tennis tournament this summer.

“It definitely feels a little bit pressuring, but I like knowing that the older kids are watching over me,” said Jayden of Bayside, Queens.

“They have high expectations, but it’s definitely not too hard on me — just knowing that we’re all a team and that we’re all just here to help each other out,” he said.

The ball boy said he was “surprised” earlier this summer when he learned he had been plucked from a pool of thousands of applicants to serve as a ball kid — a dream he’d had for as long as he could remember.

His deep-rooted passion for tennis sprouted when he first picked up a racket at age 6 to connect with his four older brothers, who were enamored with the game.

By age 10, Jayden was logging practices five days a week with the New York Junior Tennis League, and his family was capping off every summer with a trip to the US Open qualifying round.

“I would just go down there, see how fluid everything was and how everyone was together. And I thought to myself, I was like, ‘You know, one day I want to be down there. I want to be just like them,’ ” Jayden said.

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“I really felt that I had that ability just to play with them. And I had the skills to be in front of the top tennis players. I’m just really excited that I got selected.”

Akari Wientzen’s first year as a ball girl was when Italy’s Jannik Sinner took home the top men’s trophy last year at the facility’s centerpiece arena, Arthur Ashe Stadium.

Akari, 17, had originally requested off that day to prepare for her upcoming SATs — until Kitson called her and specifically asked her to work.

“Obviously I skipped SAT prep!” said Akari of Murray Hill in Manhattan.

“I couldn’t believe that I was able to do that match. And it’s what I’m most proud of in my whole life — to be able to say that I worked the men’s finals is really cool.”

Akari herself first picked up a racket at 6 years old during an after-school program — and it was love at first swing.

She now plays for Junior Tennis, as well as her varsity team at Bronx Science High School.

For Olivia Chin, her four years on the Ball Crew have brought valuable life lessons along with lifelong friendships.

For her second year in 2023, Olivia, 18, was honored to serve as a member of the all-female Ball Crew on the court when fellow teenager Coco Gauff smashed her way into the history books.

“The whole year’s theme was to honor Billie Jean King and her fight for equal prize money in tennis. I was chosen to be part of the all-female ball crew for the women’s finals championship and, wow, it was just so empowering,” said Chin of Bayside.

“Billie Jean King came up to talk to us after the match had ended, and she explained to us what it was all for, and just getting to see so many confident females on court, getting to be on court with them too, it was just so empowering. It was amazing.”

The moment was a dream come true for Chin, whose parents had been taking her to the stadium since she was an infant.

While the US Open lasts three weeks every year — which some extra days tacked on for Ball Crew training — Chin emphasized that she leaves every tournament with a trove of memories and new friends from across the globe.

“It’s just an incredible team. The sense of camaraderie is really there,” she said. “Our culture motto is: One team, one dream, and it’s really something that we live by.

“I know that if I look at anyone on the crew, they’ll have my back on or off the court and I feel that same responsibility towards them. And it’s just a blast. Ball Crew is so special.”