There is still no test for the degenerative brain disease CTE, which was found in a number of former NFL players after they died.
The latest revelation came Thursday when Patriots tight end Aaron Hernandez, a convicted murder who committed suicide in April, was found to have CTE, a lawyer for the family revealed.
On Friday, former Chiefs running back Larry Johnson said he believes he has CTE, which stands for chronic traumatic encephalopathy.
Physician Eugene Gu tweeted: “Aaron Hernandez had advanced CTE. The NFL must address this devastating occupational health hazard for all its players.