The story Nico tells Scott about why he was unable to fight in the UFC is based on actor's (Bas Rutten) own experiences. Shortly after beginning his career with UFC, while training for his third fight, he blew out his knee, as well as sustained other injuries forcing him to retire.
When Nico is trying to train Scott in his gym prior to his second fight, Nico mimics punching Scott, calling out "Liver shot" at one point. Bas Rutten (Nico) became well known during his fighting career for favoring punches and kicks to the liver of his opponents.
Near the beginning of the film, Scott Voss is "teaching" his class, and puts a newspaper over his head. On the paper is a photo of a hockey player with the headline "Season Suspended", suggesting a suspended hockey season. When this film was released in the Fall of 2012, there really was a suspended hockey season due to a player lockout.
Reactions shots for the MGM Grand fight were filmed at the old Everett, Massachusetts High School, which Ellen Pompeo graduated from in 1987 and was also used as a base camp for filming of Boston's Finest (2010).