The Calcium Kid (2004)

Jimmy Connelly, an English bachelor milkman, 'accidentally' knocks down his boxing club's champion as stand-in sparring partner. The champ was scheduled for a title fight against the reigning, American world champion. So the sleazy manager decides to substitute him with Jimmy, who is now groomed for stardom. Naive Jimmy does everything the crook says, only to be blamed when it all explodes in their faces big time. Will he keep taking it or stand his ground before his whole career and private life are ruined?