The British star, who worked with the director on the new 'Star Trek' series, tells Vulture magazine, "Well, JJ uses me in different roles, and we're good friends.
"I feel like my face in 'Star Wars' would pop people out of the movie. Look, I love Star Wars, and I don't want people to watch and go, 'Oh, there's Simon Pegg's face'.
"The film is cleverly cast with these amazing, unknown actors."
Simon Pegg has been spotted visiting the set, and his friend Benedict Cumberbatch had hinted that he would be in the film, reports he is quick to dampen.
He says, "Of course I visited the set. It's amazing, and I love Star Wars. I want to see everything happening.
"It looks wonderful, and you need to believe those characters. Any type of stunt casting might just pop you out of the movie."
Looks like we'll just have to wait and see if Simon Pegg's features are recognisable in the film, but we know it does include John Boyega, Daisy Ridley, Adam Driver, Oscar Isaac, Andy Serkis, Domhnall Gleeson, Lupita Nyong'o, Gwendoline Christie and Max von Sydow, alongside veterans Mark Hamill, Carrie Fisher, Harrison Ford and Anthony Daniels.
Filming has had to be suspended while Harrison Ford continues to recover from a broken ankle, sustained during filming of the epic at Pinewood Studios, when the door of the Millennium Falcon fell on him.
The film is due in cinemas in December 2015.