The two actors were scrapping in a moving car when Reynolds made contact with the Philadelphia star's face.
Washington explains, "Ryan gave me a black eye. There's a scene where I reach over to try and choke him where I have my handcuffs on and we were flying around in the car. He wasn't actually driving the car but it just happened - as I was reaching forward he was flying back. He went, pow!
"I never had a black eye in my life but I can't say that anymore!"
And Reynolds admits he thought he'd be asked to leave the set - and the film.
He adds, "That was my early retirement... It was weird to feel my face on fire."