Gad, 32, took to Twitter to inform about the same, reported Ace Showbiz.
"Everyone please calm down. There is no truth to rumour of me playing Grimm. Besides, I'm too busy prepping to play a young Luke Skywalker," Gad tweeted.
'X-Men: Days of Future Past' scribe Simon Kinberg writes the screenplay.
'Game of Thrones' stars Richard Madden as well as Kit Harington and 'That Awkward Moment' star Michael B Jordan are among the rumored contenders for the lead roles.
The film is expected to hit theatres on June 19, 2015.