The Moon star felt the need to study Farrell's work in detail before working with him in new movie Seven Psychopaths, and Rockwell has no doubt about just how far the actor could go in Hollywood.
He tells Details magazine, "I got an idea of what his gift is as an actor. It's his vulnerability. He's got a powerful emotional instrument. I think he's really coming into his own. He's going to be a serious leading man. He could become like a Sean Connery for us."
Rockwell also admits the sober and focused Farrell he knows now is far different from the wild man he used to party with years ago at Los Angeles' fabled Chateau Marmont hotel.
The actor says, "He had a shaved head then. He's a different guy now. Older and wiser. More focused and accessible. One of the most generous - I'm kind of in love with him. I have a man crush on Colin for sure."