"Preparing for the action scenes [in King Arthur], we watched a lot of McGregor fight footage because his style was what we were after," Ritchie told The Irish Sun.
"That very intense, singular, lightning fast, juggernaut trademark technique was perfect and we modelled Arthur's physicality on that.
"We even went after him for a part in the movie but he wasn't having any of it. Was training for a fight at the time, couldn't take his attention away from that. But you can see in his presence, in his demeanour, he's got that swagger, that real appealing cockiness. It's an unmistakeable spark."
McGregor has been attached to several potential movie roles while watching his star power rise in the UFC over the past few years, but he's maintained that his focus stays on fighting more than anything happening in Hollywood.
Rather than starring in films, McGregor has inked several lucrative endorsement deals where he's done commercials and other advertisements, but it seems for now he's not ready to try out acting - at least when it interferes with his training schedule.
McGregor did lend his image to the most recent "Call of Duty" game but still hasn't made his big box office debut.
McGregor is currently embroiled in negotiations for a mega-fight with Floyd Mayweather that could net him a nine-figure payday so it's not likely he'll be accepting any movie roles in the near future either.
