She said: "All I can say is that I had to fight someone else in this film, and they beat the crap out of me in stunt rehearsals. I have to say I could not believe it.
"I was like, 'Can you hold it back, OK? You know, I'm trying to work it out here. I've got smaller muscles than you'. I was dragged across the [floor]. When we finally finished that scene I was just happy to be alive."
A new clip from the forthcoming The Avengers comic book adaptation was released yesterday - and the film will be in cinemas from May 4.
It co-stars Robert Downey Jr, Chris Evans, Chris Hemsworth, Tom Hiddleston, Mark Ruffalo and Samuel L Jackson - so they must all be suspects as Scarlett's mystery assailant.