Messages of support poured in for Alex Ferguson after the former Manchester United manager was left fighting for his life following emergency surgery for a brain haemorrhage on Saturday.
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 Scotsman, the most successful manager in British football history.
"Sir Alex Ferguson has undergone emergency surgery today for a brain haemorrhage," the statement said. "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."
According to the Daily Mail, an ambulance was called to the Scot's home in Cheadle, near Manchester, in northwest England at 9am local time (noon UAE) on Saturday.
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 League One match against Wigan on Saturday 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 Mr 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 at Doncaster today," the former England manager added. "I hope he has a full recovery."
Southampton manager Mark Hughes, who made his name in football as a United striker during the early years of Ferguson's time 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, perhaps the most high-profile player Ferguson managed at Old Trafford, 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."
Former United striker Wayne Rooney said on Twitter: "Get well soon Boss. Thoughts with all the family at this sad time. #AlexFerguson."
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There was a particularly heartfelt message from Edwin van der Sar and his wife, Annemarie.
Van der Sar who was United's goalkeeper when Annemarie, suffered a brain haemorrhage in 2009 from which she has since recovered.
"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.
Michael Carrick, a current United midfielder, said he was "absolutely devastated".
He added: "All my thoughts and prayers are with him and his family. Be strong Boss."
The sympathy extended beyond those with United connections, with Vincent Kompany, the captain of recently crowned English champions Manchester City, summing up the mood of many messages from rival clubs when he said: "Hang in there Sir Alex. Thoughts are with the family and close ones."
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 when he stepped down as United manager, having won a staggering 38 major trophies in just over 26 years in charge, including 13 Premier League titles and two European Champions League triumphs during his time at Old Trafford.
He was back at United's home ground last week to present a commemorative vase to old rival Arsene Wenger, who steps down as Arsenal manager at the end of the season.
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.
Prior to arriving at Old Trafford, Ferguson, enjoyed considerable success as manager of Aberdeen, helping interrupt Glasgow giants Celtic and Rangers' Old Firm dominance of Scottish football.
Ferguson, a former Rangers striker, won three Scottish championships, four Scottish 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 of Ferguson's time in charge a 1999 treble of Premier League, Champions League and FA Cup titles all in the one season.