Leonardo Dicaprio missed out on playing James Dean because he looked like "a young kid".

Director Michael Mann has revealed that, before he helmed his 1995 classic 'Heat', he was attached to direct a biopic about the 'Rebel Without a Cause' star - who died aged just 24 in a car accident in September 1955 - and though the 'Wolf of Wall Street' actor had a "quite amazing" screen test for the lead role, the then-19-year-old hunk was ultimately deemed too young for the part.

Michael told Deadline: "It was a brilliant screenplay. And then it’s [the question of] who the hell could play James Dean? And I found a chap who could play James Dean, but he was too young. It was Leo.

"We did a screen test that’s quite amazing.

"From one angle, he totally had it with him. I mean, it’s brilliance. He would turn his face in one direction and we see a vision of James Dean. Then he’d turn his face another direction and it’s no, that’s a young kid."

The director felt the 'Once Upon a Time in Hollywood' star would be perfect for the project in three years time but he himself ultimately decided to move on to work on 'Heat' instead because he couldn't imagine shooting the biopic without Leonardo.

He added: "He, respectfully, undid the James Dean bio for me."

While Leonardo missed out on the biopic, he was then cast as the male lead opposite Claire Danes in 1996's 'Romeo and Juliet' and became a household name the following year thanks to his performance in 'Titanic'.

To date, the Oscar-winning actor has never worked under the direction of the 79-year-old filmmaker, though Michael did serve as a producer on his 2004 movie 'The Aviator'.