Alex Ferguson hailed Eric Harrison as one of the "greatest coaches of our time" after the former Manchester United youth team boss and mentor to the much-vaunted Class of '92 died at the age of 81.
Harrison, responsible for forging the fledgling careers of David Beckham, Ryan Giggs, Nicky Butt, Paul Scholes and Gary and Phil Neville among others, was diagnosed with dementia four years ago.
"Eric's contribution to football and not just at Manchester United was incredible," said former manager Ferguson.
"When I came as manager I was lucky enough to have Eric on the staff as head of youth development, so I got to see the work he did and not just with the Class of 92 but with all the young players.
"He built character and determination in those young players and prepared them for the future. He was a teacher, he gave these players a path, a choice and he only did that through his own hard work and sacrifice.
"He was able to impart that education to the young which made him one of the greatest coaches of our time."
Appointed by then United manager Ron Atkinson in 1981, Harrison spent 27 years at the club, 17 in charge of the youth team, and oversaw the development of a number of other high-profile youngsters, including Mark Hughes and Norman Whiteside.
His greatest success came under Ferguson with the Class of 92 players forming the backbone of United's treble-winning side of 1999.
In a statement, United said: "Manchester United is extremely saddened to report that our former youth coach Eric Harrison passed away on Wednesday. He was 81.
"Everyone at Manchester United sends their deepest condolences to Eric's family and friends at this sad and difficult time."
"We've lost our mentor, our coach and the man who made us," Gary Neville tweeted.
"He taught us how to play, how to never give up, how important it was to win your individual battles and what we needed to do to play for Manchester United Football Club. Eric we owe you everything."
Former England captain Beckham, who along with other members of the Class of '92 did not forget him in his years battling dementia visiting him at home, posted his tribute on Instagram.
"He made us understand how to work hard and respect each other and not just on the pitch. We won't forget the life lessons he gave us."
Giggs hailed Harrison, who also spent four years as Wales assistant manager under Hughes, as one of his biggest influences in the game.
"I've known Eric since I was 13 and he was a big part of my career," said the Wales manager in a statement.
"A great man and a tough coach, he instilled in us the principles of the game."