News of his operation was made public by his old club, with a United statement cautiously optimistic about the prospects for the 76-year-old, the most successful manager in British football history.
"Sir Alex Ferguson has undergone emergency surgery today for a brain haemorrhage," the statement said.
Sir Alex Ferguson has undergone surgery today for a brain haemorrhage. The procedure has gone very well but he needs a period of intensive care to aid his recovery. His family request privacy in this matter.
— Manchester United (@ManUtd) May 5, 2018
Everyone at Manchester United sends our very best wishes. pic.twitter.com/SDoNzMwVEZ
"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.
"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."
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.
— Manchester United (@ManUtd) May 5, 2018
An ambulance was called to the Scot's home in Cheadle, near Manchester, in northwest England at 9:00 am (0800 GMT) on Saturday, reported the Daily Mail.
Concerns for Ferguson's health started to mount when it was announced his son, Darren, the manager of English third-tier club Doncaster, would miss his side's match against Wigan because of "family reasons".
"It is tragic. I am going to find out how he is as soon as I possibly can," said Everton manager Sam Allardyce, a longstanding friend of Ferguson's, after his side's 1-1 Premier League draw at home to Southampton.
"Obviously I knew it was extremely serious when I knew his son Darren didn't attend his own game," the former England boss added. "I hope he has a full recovery."
Southampton manager Mark Hughes, a United striker during Ferguson's early years at Old Trafford, said: "I only just got a little whisper earlier on. I was hoping it wasn't true. I wish him all the best."
David Beckham was among several United players past and present who took to social media to offer their support to "the boss".
On Instagram, with a picture of him as a youngster alongside Ferguson, Beckham wrote: "Keep fighting Boss.. Sending prayers and love to Cathy and the whole family x @manchesterunited."
https://www.instagram.com/p/BiaKgdJHL_5/?hl=en&taken-by=davidbeckham
Real Madrid superstar Cristiano Ronaldo, signed by Ferguson as an 18-year-old in 2003, tweeted a picture with his former mentor. "My thoughts and prayers are with you, my dear friend. Be strong, Boss!" he said.
https://www.instagram.com/p/BiaW8rnlXQF/?hl=en&taken-by=cristiano
Former United and England captain Wayne Rooney said on Twitter: "Get well soon Boss. Thoughts with all the family at this sad time. #AlexFerguson."
Get well soon Boss. Thoughts with all the family at this sad time. #AlexFerguson
— Wayne Rooney (@WayneRooney) May 5, 2018
There was a heartfelt message from former United goalkeeper Edwin van der Sar and his wife Annemarie, who herself recovered from a brain haemorrhage in 2009.
"Devastated about the news about Sir Alex and knowing all too well about the situation ourselves. Stay strong and hope together with everyone you recover. Edwin & Annemarie," said the couple's Twitter post.
Devasted about the news about Sir Alex and knowing all to well about the situation ourselves. Stay strong and hope together with everyone you recover. Edwin & Annemarie pic.twitter.com/aaxqRI9Bg7
— Edwin van der Sar (@vdsar1970) May 5, 2018
Another former United goalkeeper Peter Schmeichel tweeted simply: "Please. Be strong. Win this one" interspersed with prayer emojis.
Please🙏 Be strong🙏Win this one🙏
— Peter Schmeichel (@Pschmeichel1) May 5, 2018
Midfielder Michael Carrick said he was "absolutely devastated", adding, "All my thoughts and prayers are with him and his family. Be strong Boss."
Absolutely devastated to hear about Sir Alex being unwell in hospital. All my thoughts and prayers are with him and his family. 🙏🏻🙏🏻🙏🏻🙏🏻 Be strong Boss xx
— Michael Carrick (@carras16) May 5, 2018
Vincent Kompany, the captain of new English champions Manchester City, summed up hundreds of messages from rival clubs and from right across the football spectrum when he said: "Hang in there Sir Alex. Thoughts are with the family and close ones."
Hang in there Sir Alex. Thoughts are with the family and close ones.
— Vincent Kompany (@VincentKompany) May 5, 2018
Away from football, Nicola Sturgeon, the First Minister of Scotland, tweeted: "My thoughts are with Alex Ferguson and his family - wishing him a full and speedy recovery."
Ferguson retired five years ago having won a 38 major trophies in just over 26 years in charge at Old Trafford, including 13 Premier League titles and the UEFA Champions League twice.
Ferguson recovering in hospital following brain surgery
He was at United's home ground a week ago to present a commemorative vase to old rival Arsene Wenger, who is stepping down as Arsenal manager.
Ferguson had planned to retire at the end of the 2001/02 campaign but changed his mind after speaking to his wife Cathy and their family.
But the death of his wife's twin sister in 2012 provided Ferguson with what he later wrote was a "watershed moment.
"I felt that, after all those years during which Cathy had put me first, it was time that I took care of her needs," he explained.
Manchester United face Pogba dilemma
Prior to arriving at Old Trafford, Ferguson, enjoyed success as manager of Aberdeen, interrupting Glasgow giants Celtic and Rangers' Old Firm dominance of Scottish football by winning three league championships, four domestic Cups and the 1983 European Cup Winners' Cup in charge of the Dons.
It was a similar story at Old Trafford, where his United teams ended Liverpool's dominance of the domestic game, with the highlight being the 1999 treble of Premier League, Champions League and FA Cup.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ