Joe Greb has a small and uncredited role as a brain-damaged boxer who gives an interview about the damaging effects of the sport. In reality, Greb had a 12 year career as a boxer and fought in 119 bouts during that period. Greb suffered irreparable brain damage from his time as a boxer and was a vocal proponent of fighter safety. In essence, he plays himself in this film.
Humphrey Bogart was not a fan of working with Rod Steiger. Bogart was critical of Steiger's method acting technique, and confided to a friend that "This scratch-your-ass-and-mumble school of acting doesn't please me."
Primo Carnera unsuccessfully sued the film's makers, claiming it damaged his reputation for implying that he was involved in fixed fights. Carnera's career is one of the biggest mysteries in boxing, as many of the sport's historians believe that, without Carnera's knowledge, his managers paid most of his opponents to throw their fights.