How Emma Stone picked up Billie Jean King's game for 'Battle of the Sexes'

Emma Stone and Steve Carell in a scene from "Battle of the Sexes," which releases on Sept. 22. Twentieth Century Fox Film Corporation

Kaitlyn Christian didn't expect to be in a movie, but there she was gripping a wooden tennis racket attempting to mimic Emma Stone, who was morphing into former women's No. 1 Billie Jean King for the "Battle of the Sexes" biopic film. The movie recalls the 1973 tennis match between King and former men's No.1 Bobby Riggs and releases on Sept. 22.

Christian, Stone's stunt double, was tasked with helping the Academy Award-winning actress play King's game.

Former ATP Tour professional tennis player Vince Spadea served as the film's tennis choreographer and doubled for actor Steve Carell, who plays Riggs. Christian and Spadea worked together to make the tennis in "Battle of the Sexes" believable.

Carell wasn't an expert but was well-versed on the game. The actor best known for "The Office" even has a home court. Stone was a novice.

"It was fun to spend some time on the court with [Emma]," Christian said. "We got to practice a lot and spend a lot of time shadowing different strokes." Spadea and Christian helped Stone perfect her form and emulate King's tennis strokes.

King came out to the practice court to provide some pointers on things such as how she bounced the ball and tossed it before a serve.

Spadea and Christian received the scripts and some direction throughout production, but they also played points naturally to figure out what would work best on film. They didn't want it to look contrived, but the ball also had to land in particular locations to match reference clips. On top of all of that, they were never playing as Spadea and Christian but rather as Stone and Carell playing King and Riggs. Not to mention the wooden rackets.

"The sweet spot on that [wooden] racket is so much smaller," Christian said. "You have to be more disciplined with your feet, with your hands, and where you hit the ball. I think it helped my real tennis game out."

Stunts happen in nearly every film, whether someone jumps through a window or rides a motorcycle or hits a tennis ball. In the case of "Battle of the Sexes," the film tells a nonfiction story, and though it will certainly be dramatized, the match between King and Riggs did happen in real life.

"You're mimicking true artistry, the two best players in the world at the time, and that's not easy," Spadea said.