Sir Alex Ferguson is fighting for his life in hospital after undergoing emergency surgery for a brain haemorrhage.
The legendary former Manchester United boss, 76, was taken to Salford Royal Hospital with a police escort after he was initially taken to Macclesfield district hospital on Friday morning.
His son Darren - manager of League One side Doncaster Rovers - missed his final game of the season on Saturday to be with his dad.
And the great and good of the footballing world shared their well-wishes for Ferguson who is said to have complained of being unwell since Thursday.
A statement from United read: "Sir Alex Ferguson has undergone emergency surgery for a brain haemorrhage.
"The procedure has gone very well but he needs a period of intensive care to optimise his recovery. His family request privacy in this matter."
The club later added: "We will keep Sir Alex and his loved ones in our thoughts during this time, and we are united in our wish to see him make a comfortable, speedy recovery."
The football community came together to send their well-wishes to Ferguson, upon hearing the news.
David Beckham, perhaps the most high-profile former player of Ferguson's United reign, offered his support, posting a picture on Instagram of him signing a contract as a teenager alongside Ferguson.
Accompanying the picture was the message: "Keep fighting Boss.. Sending prayers and love to Cathy and the whole family x @manchesterunited"
Cristiano Ronaldo, who rose to prominence under Ferguson, said: "My thoughts and prayers are with you, my dear friend. Be strong, Boss!"
United club captain Michael Carrick said he was "absolutely devastated" by the news, while Mike Phelan, who played under Ferguson for United and later served as his assistant, wished his former boss a swift recovery.
Former United forward Wayne Rooney, who now plays for Everton, gave his support to the Ferguson family, tweeting: "Get well soon Boss. Thoughts with all the family at this sad time. £AlexFerguson"
Goalkeeper Peter Schmeichel, who was part of United's treble-winning team in 1999, posted: "Please Be strong Win this one", and Ashley Young, whom Ferguson brought to Old Trafford in 2011, spoke of his shock.
"Gutted to hear the news tonight about Sir Alex. Don't really know what else to say other than thoughts and prayers with you and your family, Boss," he said on Twitter.
Manchester City captain Vincent Kompany said: "Hang in there Sir Alex. Thoughts are with the family and close ones."
And Gary Lineker wrote: "Very sorry to hear the news that Sir Alex Ferguson is seriously ill in hospital. Wish him all the very best."
Everton boss Sam Allardyce spoke to the press ahead his side's late draw with Southampton on Saturday, saying: "It's tragic. I am going to try to find out how he is as soon as I can.
"I hope he's in good hands and that the operation is a major success. I know it was bad when his son Darren missed the Doncaster game.
"Now Manchester United have confirmed he has had a bleed on the brain. He is a personal friend and I hope he has a full recovery."
Sir Alex was in fine spirits at Old Trafford a week ago when he appeared pitchside before United's game against Arsenal.
