Andre Waters

Waters was regarded as one of the league's hardest-hitting defensive backs during his career with the Philadelphia Eagles. But he committed suicide in 2006, at the age of 44. An autopsy showed that his brain tissue to be similar to that of an 85-year-old's Alzheimer's patient, Dr. Omalu told the New York Times. "If Waters had lived another 10 to 15 years, he would have been "fully incapacitated," Dr. Omalu told the newspaper.

Credit: Gene Sweeney /Allsport