And to make matters worse, one of his movie opponents knocked the movie fight co-ordinator out during rehearsals, minutes before cameras rolled.

"All the boxers in the movie were real boxers," the Whiplash star tells WENN. "The first fight in the movie, I had five days to rehearse with the fight co-ordinator. The second fight a day and a half and the third fight, like, a day to rehearse.

"Just before the last fight of the movie this guy who was playing (Roberto) Duran was learning the numbers and I'm talking to (director) Ben Younger and we look over and the boxing co-ordinator was knocked out! This fighter had really hit him, but we had to continue to finish the film."

Teller, who portrays real-life lightweight, light middleweight and super middleweight boxing champ Vinny Pazienza, aka Vinny Paz, in the movie, admits he has always had an appreciation for boxing, but he prefers mixed martial arts.

"I've always had a respect for fighters and some of my buddies are MMA guys and I follow that more than boxing," he explains. "MMA fighters don't get hit as much, and boxing is 12 rounds - and you gotta take some punches."

Meanwhile, his co-star Aaron Eckhart was more seasoned when it came to the fight scenes - the actor has been boxing for 20 years.

The Sully star reveals he strapped on the gloves and stepped into the ring for fitness when he had to get in shape for 2000 movie Erin Brockovich, and it has become a big part of his life ever since.

"I learned a skill to get in shape for this Hollywood career," he tells WENN. "I always say to young actors, 'You got to learn how to ride a horse, shoot a gun and throw a punch, because if you learn those things early you're going to do that in your career and you want it to look second nature'.

"I work boxing into my work-outs every single day, so if I'm doing sit-ups I always come up into a punch. Whatever I do I always incorporate boxing into it, which really helped me out in this movie."