Tomorrow's Manchester Evening News front page has the headline, "your time has come" and suggests that Everton manager David Moyes looks set to succeed Sir Alex Ferguson as Manchester United manager.
Manchester United and England midfielder Tom Cleverley has tweeted:
Sure I'm not alone saying this. Boss has been a massive influence on my career to date. Thanx and all the best!
Andy Murray, the world number three in tennis, has tweeted:
What a legend sir alex ferguson! Shame that he is retiring from management but what a career its been.. Who's next for united?#irreplaceable
Chancellor George Osborne said he remembers the time he canvassed Sir Alex Ferguson's house as a young candidate - Fergie is a lifelong Labour supporter.
Sir Alex - amazing manager & a constituent. Have memories of spectacularly unsuccessful attempt to canvass his house as a young candidate
Rio Ferdinand has become the first current Manchester United player to react to the news of Sir Alex Ferguson's retirement.
The bosses work ethic, his desire to win + to make us better players were unrivalled. Thanks boss.
The Prime Minister has paid tribute to Sir Alex Ferguson - and suggested he could now help to make "life a little easier" for Aston Villa.
The Manchester United manager announced earlier today he is retiring, after 26 years in charge. David Cameron, who is a Villa fan, said Ferguson's contribution to football has been exceptional.
Twitter said the news of Sir Alex's retirement received more than 1.4 million mentions in the first hour after the story broke at 9.18am.
It compares with one million mentions in the four hours after the death of Lady Thatcher was first announced last month.
The original tweet from Manchester United was retweeted or made a favourite tweet more than 18,000 times, while the official club hashtag #ThankYouSirAlex had more than 100,000 mentions within the hour.
Former Manchester United midfielder David Beckham has posted the following tribute to Sir Alex Ferguson on his Facebook page.
I've just seen the news on Sir Alex. As I have said many times before the boss wasn't just the greatest and best manager I ever played under he was also a father figure to me from the moment I arrived at the club at the age of 11 until the day I left.
Without him I would never have achieved what I have done in my career. He understood how important it was to play for your country and he knew how much it meant to me.
– David Beckham
After '98 without the manager I would have found it virtually impossible to cope with the attention I was getting on and off the field and for this I will always be grateful to him for his support and protection.
I am truly honoured to have been guided by the greatest manager in football and to have had the career that I had under him.
Thank you boss and enjoy the rest!
Barcelona's Gerard Pique, Fiorentina's Giuseppe Rossi and Portland Timbers' Mikael Silvestre - all former Manchester United players - have paid tribute to Sir Alex Ferguson on Twitter:
26 years, 13 league titles, 2 Champions Leagues, the Cup Winners' Cup, 5 FA Cups, 4 League Cups… Legend! http://t.co/33SRUiu0B3
What a career! Proud and honored to have been coached by Sir Alex Ferguson. #thankyougaffer
Chief executive of Sainsbury's and lifelong Manchester United fan Justin King said he believes Sir Alex Ferguson has given the club "27 good years" and stated his belief that staff would continue his success in the future.