I once interviewed a player who was retiring because his cognitive functions had declined so much that he often couldn't remember where he was, and had terrible mood swings, after experiencing what he said was more than ten concussions through his career. Most of them unrecorded. https://twitter.com/NathanAClark/status/1338872160388067336

The silly outlet kept trying to position the story as him saying his goodbyes and thanking the various teams he played for, and I couldn't do it without centering the fact that the man's brain had been ruined without anyone taking the problem seriously.

First concussion was when he was in his teens. Got elbowed during a header in training. Trainer made him count backwards and sent him back out. As he was driving home, he pulled over, called the coach and asked how he got on the road. Had no recollection.

As it got worse later in his career, he would find ways to avoid heading the ball in training and to suffer through the concussion protocol which includes, heading the ball to prove that you've recovered from head damage. Said he would be at home and just randomly start crying.

Found the document: