The tragic overdose death of a still young former NFL safety and Superbowl winner may have greater implications for the sport after doctors at Boston University found evidence of advanced chronic traumatic encephalopathy (C.T.E.) in his brain following an autopsy.

Iowa native Tyler Sash played for the New York Giants for two years, earning a Superbowl ring during his 2011-2012 rookie season. By the beginning of the 2013 season, however, he was released from the team after suffering yet another concussion during a preseason game. Sash, who would never see the football field again, then spent the next few years struggling to return to a quieter life before being found dead at the age of 27 on September 8, 2015, having accidentally overdosed on two powerful pain medications.

At the time, Sash’s family chalked up the mental hardships he experienced post-NFL to the pain meds he took while awaiting surgery for a chronic shoulder injury. Now it appears the lingering, repetitive brain damage caused by a more than decade long football career could have contributed as well.

“It helps explain his inattention, his short fuse and his lack of focus,” Dr. Ann McKee, chief of neuropathology at the V.A. Boston Healthcare System and a professor of neurology and pathology at the Boston University School of Medicine, told The New York Times, which first reported Mckee and her team’s findings. “Even though he was only 27, he played 16 years of football, and we’re finding over and over that it’s the duration of exposure to football that gives you a high risk for C.T.E. Certainly, 16 years is a high exposure.”

Dr. Mckee, who examined Sash’s donated brain herself, classified the extent of his C.T.E. as stage 2, the same level of severity found in another former NFL player, Junior Seau, following his suicide at the age of 43 in 2012 (there are four stages of C.T.E. in total).

Though there is still debate over how C.T.E. exactly influences a sufferer’s mental health, Sash’s family believes the diagnosis has provided them a degree of closure concerning Sash’s erratic behavior after he returned home, which included an arrest for public intoxication in 2014.

“My son knew something was wrong, but he couldn’t express it. He was such a good person, and it’s sad that he struggled so with this — not knowing where to go with it,” Barnetta Sash, Tyler’s mother, told The NY Times.“Now it makes sense. The part of the brain that controls impulses, decision-making and reasoning was damaged badly.”