Emma Stone thankful to shoot first sex scene with Andrea Riseborough

Emma Stone feels lucky to have landed actress Andrea Riseborough as her partner for her first movie love scene in Battle Of The Sexes.

The La La Land star portrays Billie Jean King in the new film, which revolves around the tennis great's famous 1973 exhibition match with Bobby Riggs, played by Steve Carell.

Battle of the Sexes also required Emma to get hot and sweaty between the sheets, as the story line explored King's lesbian love affair with hair stylist Marilyn Barnett - the Oscar winner's first intimate scenes onscreen.

Emma admits working with the British actress, who was cast as Marilyn, made her debut sex shoot a breeze.

"I couldn't be luckier," she gushed to Vanity Fair at the Toronto International Film Festival on Sunday (10Sep17). "She is truly the most transformative, incredible actor. So it was like a true lucky break on my part."

Emma also found a way to ease her nerves about stepping into Billie Jean's shoes, by deciding to keep her distance from the sports icon before and during filming.

"I didn't talk to her too much while filming because it was too much pressure and she has all the benefit of hindsight of decades older now," the 28-year-old said. "But it was really scary at first."

The pressure to perform was compounded by the fact that Emma isn't naturally sporty, so she had to work for months to overcome her lack of co-ordination to accurately portray Billie Jean on the big screen.

"We quickly learned that the choreography would be the most important thing, because learning how to do a serve or backhand like Billie Jean was more of an impossible dream than a reality," she shared. "This was the first time where I really thought through the physicality (of a character)... Once I felt more physically able, I would be able to develop more of the interior life of her. There was a lot of bulking up, tennis lessons, learning her stance, and feeling my way into her body. She is a machine."

Emma has since had the chance to really get to know Billie Jean in person, and even joined her courtside at the U.S. Open Women's Final in New York on Saturday (09Sep17), where the two women watched Sloane Stephens beat Madison Keys in two sets to land her first major trophy.

"(We) went to the U.S. Open together yesterday, and she was catching and throwing balls," Emma recalled."I was like, 'This is like the easiest s**t to you... to be throwing a ball.' But that alone took me months to learn. It was my first time at a live tennis event, and she was commenting in my ear. It was just amazing."

Prior to the championship match, Emma joined singer Sara Bareilles to take part in an on-court ceremony honoring Billie Jean on the 50th anniversary of her triple win at the event, where she won the women's singles, women's doubles, and women's mixed doubles titles back in 1967.

Bareilles' new song If I Dare features on the soundtrack to Battle of the Sexes, which opens later this month (Sep17).