Williams, who played 250 games with Geelong, the Sydney Swans and Carlton between 1984 and 1997, has told Channel Seven's Sunday Night program he can't remember large chunks of his career.
That includes Grand Final day 1995, when the prolific onballer kicked five goals to win the Norm Smith Medal in a Carlton victory.
"Obviously I know that I won the premiership in 1995 and things like that, but I don't remember a lot about the game, no I don't," Williams said.
"I know I started '84 at Geelong, '86 I can remember, all those main dates, and the Grand Final loss in '93 and won the Brownlow in '94.
"But the specifics as you say, like the Grand Final after the game in the rooms, I remember nothing about that."
A newspaper report on Sunday said Williams has been found to be suffering symptoms of chronic traumatic encephalopathy (CTE), a condition commonly found in athletes from contact sports who have experienced head knocks.
The retired star, who now manages a golf course near Barwon Heads in Victoria, has been participating in CTE testing at Deakin University alongside five other former AFL players and one former NRL players.
All seven have shown symptoms of brain disease.