The phrase "Madden curse" refers to a supposition that involves the "Madden NFL" game series. It purports that any player who appears on the cover of a game in the series ends up cursed, which normally entails injuries and poor performance on the field.
The legend started off as a simple joke in 1999 but has since grown into a full-blown superstition. Fans often campaign to keep the stars from their teams from appearing on the cover. The phenomenon is so widely recognized and popular that the gambling world posts odds every year regarding the possibility of a player featured on the Madden NFL cover suffering an injury during the following season.