The writer and director met both actors in Los Angeles and came away from the get togethers convinced Statham was the man to play brutal Birmingham, England, crime boss Tommy Shelby.
He tells Esquire, "One of the reasons was because physically, in the room, Jason is Jason."
But Murphy helped to change his mind with a text, which read simply: "Remember, I'm an actor."
"Cillian, when you meet him, isn't Tommy, obviously, but I was stupid enough not to understand that," Knight adds. "He can transform himself. If you meet him in the street he is a totally different human being."
Production on the sixth season of "Peaky Blinders" was set to start as the coronavirus pandemic shut down the film industry in the U.K.