Paul Newman opposed sound looping the picture, stating it interfered with the actors' performances, so a small (for that time) chest microphone was developed that eliminated around eighty percent of dialog looping, and saved its associated post-production costs as well.
Paul Newman was concerned about his accent, so he spent two weeks in Mexico with dialect coach Walon Green.
Paul Newman wore a prosthetic nose for his character, and MGM shipped two of them each day to the filming location.
Martin Ritt was previously involved, in the developmental stage, with Die glorreichen Sieben (1960), which was also a remake of a film by Akira Kurosawa.