The movie based on the popular video game franchise from Blizzard is already set to be directed by Moon filmmaker Duncan Jones.
Deadline reports that Farrell has been offered a lead role in the film, while Patton is currently in negotiations to sign on.
Sources claim that Farrell is not yet decided on whether to take the part, while Jones is actively auditioning other actors for main roles.
Shooting for the film, which will be titled Warcraft, begins in January.
Farrell will next be seen later this year in Winter's Tale, while Patton stars opposite Octavia Spencer and Derek Luke in the romantic comedy Baggage Claim later this fall.