Sir Alex Ferguson has changed the art of football management forever, the head of the League Managers' Association believes.
Richard Bevan, chief executive of the LMA, paid a glowing tribute to the Manchester United boss just hours after he announced he would retire at the end of the season following 26 years in charge of the club.
"Sir Alex has left an indelible legacy not only at Manchester United but on the art of football management itself," Bevan said of a man whose managerial career began with East Stirlingshire in 1974.
"38 major trophies in 26 years in charge of the club is a record that simply speaks for itself.
"It's not just his longevity in the game, at one of the world's biggest and most demanding clubs which is remarkable, rather it has been his ability to consistently deliver the highest levels of success throughout his 40 years and over 2,150 matches in football management.
"What Sir Alex has achieved personally with both Manchester United and Aberdeen, where he broke the Old Firm stranglehold in winning 10 trophies in seven years before his appointment at Old Trafford, is unrivalled.
"At the LMA we are also extremely grateful for the amount of time and dedication he has willingly provided to our association and our members since he first joined in 1986.
"As he retires as the most successful manager in the history of the British game we congratulate him on a magnificent career and wish him all the very best for the future."
Howard Wilkinson, chairman of the LMA said: "Today's news draws to a close the career of a man and a manager, the likes of which we will never see again.
"His public face was always that of the ultimate professional with a fierce pride and determination to do the very best for his club. His frighteningly competitive nature has never nor ever will be equalled.
"He is the epitome of the mantra: 'Survive, Win, Succeed'. But, in private, with those he trusted, he was the very best sort of friend you could ever wish for.
"To say his presence on the bench will be sorely missed in no way begins to describe the massive hole he will leave behind. He always said he was too old to retire, let's hope he manages to enjoy the retirement he deserves."