Barnsley-born Winstanley - an outstanding youth talent who played for the Barnsley Boys team which won the Yorkshire Shield in 1960 - joined his hometown club in the early Sixties, signing a professional contract in May, 1962 and made his debut at the age of just 17.
The redoubtable centre-half, commanding in the air and known for his superb reading of play, made 461 appearances for the Reds and is third in the club's all-time appearance list behind Phil Chambers and Barry Murphy, with his haul of 39 goals being a record for a Barnsley defender.
Winstanley was handed the Reds' captaincy at the age of just 19 at the start of the 1964-65 season and is the youngest player to lead Barnsley in the club's history.
He also played four times for England's youth team.
Winstanley produced a famous performance against Watford in 1969 when, with the Reds 2-0 behind at Oakwell, he went up front and scored an outstanding, match-winning
Winstanley left Oakwell to join Chesterfield in 1973 and made over 100 appearances for the Spireites and after ending his playing career, he enjoyed a long and successful 24-year spell on the Reds' coaching staff.
Alongside earning an outstanding reputation for developing young players, Winstanley is fondly remembered as the much-valued assistant to Danny Wilson during the club's historic promotion to the top-flight in 1996-97 and later spent two brief spells as caretaker manager in 1998-99 and 2000-01.
He was given a testimonial match by the club in November, 2001 against Manchester United, when Sir Alex Ferguson showed a mark of respect by fielding the likes of Ryan Giggs, World Cup winner Laurent Blanc, Ole Solskjaer, Dwight Yorke and Dennis Irwin in a crowd of 7,500.
Winstanley also served as a technical director of the Saint Kitts and Nevis national team and had subsequent spells as youth team coach at Doncaster Rovers, assistant manager to ex-Reds captain Neil Redfearn at Scarborough and head of youth development, assistant manager and head coach at York City, alongside another former Barnsley player in Colin Walker.
A regular at Oakwell in his later years, Winstanley was invited to the club's inaugural Oakwell Hall Of Fame ceremony in 2018 and received the Local Hero Award for his contribution to the local community.
He was due to be inducted into the Oakwell Hall Of Fame outright in the summer, with the club saddened that it will now take place posthumously.
A club statement read: "Barnsley Football Club is devastated to learn of the passing of the legendary Eric Winstanley
"Eric Winstanley is a name that will forever be synonymous with Barnsley Football Club.
"As a club, today's news hit hard. It's impossible to get across just how impactful one man can be on this club we all adore.
"As a club, our thoughts are with his partner, Debra, his sons Andrew and Mark and with his grandchildren at this difficult time.
"We are in dialogue with the relevant bodies as we look to pay our respects to Eric Winstanley in the best way possible this Saturday when we take on Swansea City in the Sky Bet Championship play-off semi-final second leg at Liberty Stadium."