To film the final fight, the seats were filled with 15,000 blow-up dummies with masks and hats.
Professional boxers played Jimmy Braddock's ("James J.") opponents. They were told to land their blows as close to Russell Crowe's body as possible. Unfortunately, they sometimes couldn't pull back in time and ended up injuring Crowe.
Rosemarie DeWitt (Sara Wilson) is the granddaughter of the real Jimmy Braddock ("James J."). She is the daughter of his daughter Rosemarie, who was portrayed by Ariel Waller in this movie.
Filming the boxing sequences was so brutal, Russell Crowe said that this movie was "four to five times more difficult than Gladiador (2000)."