Bobby Charlton hailed Alex Ferguson as "sensational" after the Scot announced his retirement as Manchester United manager at the end of the season.
Charlton was one of the United directors who appointed Ferguson in 1987 and he said: "He is such a fantastic manager. Everything he has done has been fantastic. He is a sensational person in every form and I am really delighted for him.
"I am a director, but I hardly do anything because we are winning all the time and it is all down to Sir Alex Ferguson. He would get up in the middle of the night and travel 300 miles if he thought there was a schoolboy that he could sign." Fellow United old boy Bryan Robson was another surprised by the decision of the man he will always call 'the boss'.
"It definitely came as a surprise," he said. "It would have to happen at some stage and I think the boss must have just felt he has got a lot of grandkids and maybe he wanted to spend a bit more with them."
Red Devils defender Rio Ferdinand also lauded 'boss' Ferguson, tweeting: "The bosses work ethic, his desire to win + to make us better players were unrivalled. Thanks boss."
Former United players also took to Twitter to pay their respects.
Cristiano Ronaldo tweeted a picture of himself and Ferguson on the day he joined Manchester United in 2003, adding: "Thanks for everything, Boss."
Dutch striker Ruud van Nistelrooy also tweeted a picture saying: "2001-2006, 219 games,150 goals under the most successful manager in football history. It was a unique privilege."
Former United keeper Peter Schmeichel described Ferguson's decision to retire as a "bombshell". "I'm shocked – I just can't make sense of the timing," he said. "It has come as a bombshell, I really don't know what to make of it.
"Yesterday I was really happy with what he had done this season, now this, I'm disappointed and very sad."
UEFA president Michel Platini described Ferguson as "a true visionary".
Platini said: "His dedication, his attention to detail and his unique eye for talent, as both the manager of Manchester United FC and Aberdeen FC, has brought rich rewards over a 30-year period. He is a true visionary."