Former England captain Dave Watson has a neurodegenerative disease that was "most likely" brought on by head injuries and repeated heading of the ball during his playing days, his wife has said in a statement.
Penny Watson says that the 73-year-old's consultant thinks that it is "in all probability Chronic Traumatic Encephalopathy" - the disease determined as the cause of former West Brom striker Jeff Astle's death in 2002.
Watson shone as Sunderland won the FA Cup in 1973 and helped Manchester City to League Cup glory three years later in a career that saw him play for a variety of clubs and represent his country on 65 occasions.
The former defender will be inducted into Sunderland's Hall of Fame next month - ahead of which wife Penny has revealed he is dealing with a neurodegenerative disease.
In a statement released to the PA news agency, she said: "Now seems like the right time to inform you that for several years my husband Dave Watson, former England football international player and captain, has been battling a neurodegenerative disease.
"His consultant has concluded that the condition Dave is now living with is in all probability Chronic Traumatic Encephalopathy (CTE) - most likely caused by Dave's many head injuries, including severe concussions, and repeated heading of the ball.
"Dave has good days and bad days. He endeavours to continue to live and enjoy a normal life, as best as possible, however almost every day we are confronted with a new challenge.
"If you come across him at a match or elsewhere, please don't be afraid to interact with him. Understand that he may not be able to converse in the way he once did, but he still loves to talk about football and share a laugh.
"Please be considerate if he is having a bad day and struggling. This disease plays tricks on his memory, so he may not be able to remember accurately, and he may find signing autographs a challenge.
"The last thing Dave wants is to be treated with pity. He has always been a fighter, as those of you who watched him play know but this is one battle Dave cannot win.
"Even though things have not ended up as we both planned, Dave does not regret pursuing his passion, doing what he loved - playing football.
"We shall not be doing interviews at this time and hope you respect that decision."
Watson represented Sunderland, Manchester City, Werder Bremen, Southampton and Stoke during his time as an England player, having made his debut in a friendly against Portugal in 1974 at the age of 27.
The Nottinghamshire-born defender was 35 when he won his 65th and final cap.
In October, a study commissioned by the Football Association and the Professional Footballers' Association found that former footballers are approximately three and a half times more likely to die from neurodegenerative disease than the general population.
The first part of the FIELD study, conducted by the University of Glasgow, assessed the medical records of 7,676 men who played professional football in Scotland between 1900 and 1976.
This week, the FA's head of medicine Dr Charlotte Cowie said the reasons for footballers being at increased risk will be the primary focus of future research.
Age-appropriate limits on the amount of heading under-18s do in training are set to be introduced by the FA.
The PA news agency understands the guidelines, which are still to be finalised, will place some restrictions on heading in youth football in England to address health fears concerning the impact of heading balls.