There's a moment in Borg/McEnroe, TIFF's opening night film, when crass tennis star John McEnroe scolds reporters for focusing on his bad behaviour, not his sport.

Eerie parallels can be drawn to Shia LaBeouf, who plays McEnroe in the film and is perhaps better known for numerous arrests, a drunken racist tirade and the puzzling performance art than for his acting. It's something that's not lost on the star.

"This is another parallel that I feel with him, for sure," he told reporters at a Thursday press conference. "It's part of the cathartic feeling of the film for me."

And though LaBeouf has never met McEnroe, he defended the tennis legend and his reputation several times during the press conference. He says was offered the chance to play McEnroe in another movie but said he passed because it didn't show "respect or any empathy" for McEnroe's story.

"He's turned into quite a sweet man. He's sort of the bad Santa of tennis. He's a very lovable guy."

Put through tennis boot camp

The film follows McEnroe and Björn Borg (played by Swedish actor Sverrir Gudnason) in the lead-up to their legendary 1980 Wimbledon showdown — long considered one of the greatest matches ever played. Borg beat McEnroe to claim his fifth consecutive Wimbledon title.

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Director Janus Metz, left to right, and actors Shia LaBeouf, Stellan Skarsgard and Sverrir Gudnason take part in a TIFF press conference for their film Borg/McEnroe on Thursday. (Chris Donovan/Canadian Press)

That memorable match is painstakingly recreated towards the film's end and required LaBeouf and Gudnason to look like they knew how to play, something neither had done before.

The pair were put through tennis boot camp months before the film started shooting, during which they played tennis everyday.

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Shia LaBeouf poses with fans as he arrives on the red carpet for Borg/McEnroe on Thursday. LaBeouf didn't talk to press on the carpet but took part in a press conference earlier in the day. (Mark Blinch/Reuters)

"You had to live that life as an athlete to understand that part," said Gudnason.

"You have to find the character within because if you just put on a headband, it's going to look uncool. But if you're grounded in your character, then it's going to fly."

Sweden's 'biggest athlete'

Both actors watched videos of old tennis matches (and in McEnroe's case, videos of outbursts) to get into character. They also drew on audio books and biographies.

Gudnason didn't meet the real-life Borg until last week, at a screening in Sweden. It's something he says he did on purpose, worried it would interfere with his interpretation.

"I thought that would help me build from all the material I could find on him ... and then do my own guesses."

The Swedish-born Gudnason was just an infant when the famous match happened but said Borg remains the "biggest athlete" his country has ever had. "Those guys were the first rock stars of tennis."

The film — directed by Janus Metz and also starring Stellan Skarsgard as Borg's coach — has no planned wide-release in North America. It will screen several more times throughout the festival, which runs until Sept. 17.