On Friday, June 3, 2011, Johnson died in Tracy, California at the age of 81. On June 9, 2011, it was announced that Johnson and his fellow "Million Dollar Backfield" teammate, Joe Perry, who died on April 25, 2011, would have their brains examined by researchers at Boston University who are studying head injuries in sports. Both men were suspected of suffering from chronic traumatic encephalopathy, a disorder linked to repeated brain trauma. According to his daughter, Johnson could not talk or swallow in the final year of his life and also was in a wheelchair. She told the San Francisco Chronicle that she hoped by donating her father's brain, it would "help with a cure."