Hockey has long been associated with brawls, but the stereotype might not be so funny anymore. Researchers at Boston University have been studying the brain of deceased former NHL enforcer Bob Probert, famous for being one of the most fist-happy players in the league for 16 years. Researchers said Wednesday they had found some disturbing evidence: The same degenerative disease—chronic traumatic encephalopathy—that has been found in more than 20 deceased professional football players and has caused the NFL to change some of its rules to try to restrict dangerous head injuries. NHL Players’ Association Executive Director Donald Fehr said the findings on Probert should be taken seriously. But fights are tricky to regulate in hockey: Even with the significant drop in brawls in the NHL, the fights are considered essential to games.