REVEALED: Coco Gauff’s coach Brad Gilbert gave tennis lessons to Zendaya and her Challengers co-stars Josh O’Connor and Mike Faist: ‘They put it in the hard yards’

Hollywood turned to legendary tennis coach Brad Gilbert to help Zendaya and her Challengers co-stars hone their skills on the field.

Gilbert is one of tennis’ most celebrated people, having worked with the likes of Andre Agassi, Andy Roddick, Andy Murray and now Coco Gauff.

The film, which hit the big screens in America this week, follows a tennis champion (Mike Faist) as he tries to make a comeback with the help of his wife, a child prodigy turned coach (Zendaya). But among the opponents standing in his way are his former best friend and his wife’s former lover (Josh O’Connor).

Gilbert, who helped Gauff win a first Grand Slam at the US Open last year, was appointed tennis consultant for the film.

During a three-month training course in Boston, he put the actors through their paces for two hours every morning.

Gilbert is one of the most celebrated tennis people and he has worked with the Hollywood stars

(L-R) Josh O’Connor, Zendaya and Mike Faist were put through their paces for the film

His job was to ‘make sure everything was as authentic as possible… all the players, the opponents, the linesmen and ball people.’

That included working with the stars and tennis pro body doubles. For example, Faist had to eat about 10,000 calories a day to get into the shape necessary for his character. Gilbert’s wife Kim also “sent them all a bunch of videos to help them understand.”

Faist’s character Art was supposed to be “this classic player with a one-handed backhand, kind of patterned after a Pete Sampras,” while Zendaya played Tashi, a “killer” on the court, and O’Connor’s Patrick “more of a this freewheeler.” ‘

“They put it in the hard yard,” Gilbert told People. ‘The focus that actors and tennis players have is similar.’

Faist, Gilbert revealed, “was the only one who had played in high school,” while Zendaya had only played a handful of times as a kid. “Josh had literally never played before,” the coach added.

Body doubles were used as Gilbert tried to ‘make sure everything was as authentic as possible’

Gilbert has worked with Andre Agassi, Andy Roddick, Andy Murray and now Coco Gauff

Training started every morning at 7am. “Then they had to work on their acting all afternoon… so we had long days getting ready to start filming,” Gilbert added.

‘Nothing is choreographed in tennis. It’s in real time’. But during the making of a film, even short rallies had to be rehearsed ’50 times’.

“I had an actor on each field practicing their routine, what they had to do, and thus learning (their) role for each of those points,” he said.

During a meeting, O’Connor was ordered to hit a tweener – a shot between his legs.

“We practiced this so much, and that was the hardest shot for Josh to make,” Gilbert recalled. “A one in a million chance.” In practice he made it happen. “I couldn’t believe we didn’t have it on film,” Gilbert added.