The Hardest Ticket at the U.S. Open? Ball Person.

Thirty minutes before the gates to Arthur Ashe Stadium opened at 4 p.m. on June 22, a cluster of people began gently rolling tennis balls across a parking lot.

One after the other, they lowered one knee close to the ground, extended their opposite arm, and released a tennis ball to someone 10 feet away.

Closer to a locked chain-link fence, a gaggle of people started doing calisthenics as others nervously shifted their weight back and forth, tightly clutching their paper applications.

The group of 500 people — already whittled down from some 1,200 online applicants — would be vying for 120 spots as ball people for the U.S. Open, during tryouts over a full week that were forced indoors because of rain. Those selected joined the 200 or so ball people who are returning to service the courts in Queens.

“I don’t think people understand, it’s a highly sought-after job,” said Tiahnne Noble, the director of the U.S. Open Ball Crew.

Ranging in age from 14 to their mid-70s, the hopefuls came from all corners of the country. Applicants flew in from California, drove from Indiana, took the subway from the Bronx and rode the train from Connecticut. Some were tennis fans, some played themselves and others had their curiosity piqued from seeing ball people on TV. Could they do that? (Spoiler: Mostly not.)

The adults were generally far more anxious than their younger counterparts. The experience was described as a “dream” by many over the age of 30.

Masami Morimoto, 59, said she had been determined to try out before she turned 60. “I love tennis,” the Manhattanite said, a bounce in her step. “I couldn’t sleep, I was so excited.”

Groups were led through a series of drills during 30-minute auditions, in which they were asked to quickly and quietly roll, retrieve and toss balls. Participants were locked in, acting as though, at any moment, Novak Djokovic would look one of them dead in the eye and motion for a ball.

Supervising staff members were highly attuned to the jitters. When an applicant forgot instructions, throwing a ball instead of rolling it, they were quick to comfort the anguished applicant. “Don’t worry about it!” they would say gently, sending a tennis ball back in their direction.

Body language suggested the message went unheeded.

Noble and her staff of veteran ball people said they could spot a potential ball person almost immediately. Ball people, she said, must have speed, agility, quick reflexes and the ability to blend into the background of the tournament.

Six ball people work each match, communicating clearly and silently so as not to distract the pros or spectators. They need to respond to the preferences of different players — some only want a ball tossed to them with their left hand, for example — and act as invisible guardians of the game.

As evaluators looked on at the tryouts in June, there was plenty of subtle nodding and note taking on clipboards.

The auditions were not for the faint of heart….