Eminem, 41, was initially slated to essay the lead role in 'Southpaw' but he pulled out of the movie to dedicate more time to his music career, reported Ace Showbiz.
Helmed by Antoine Fuqua, the movie centres on a welterweight boxer who fights to reclaim his past glory and win back the affection of his young daughter.
The project was initially developed at DreamWorks, but it was later bought by MGM and set to be distributed by Sony Pictures.
Gyllenhaal, who will next be seen in 'Enemy' and 'Nightcrawler', may portray the lead role in the movie.