Manchester City manager Pep Guardiola has sent his best wishes to Alex Ferguson for a speedy recovery.
The former Manchester United manager, 76, is seriously ill in intensive care after undergoing emergency surgery following a brain haemorrhage.
The Scot is good friends with Guardiola. Ferguson enjoyed incredible success with United, winning 38 trophies in 26-and-a-half years in charge before retiring in May 2013.
Ferguson took Guardiola out to dinner just two weeks ago to congratulate him on winning this season's Premier League title with City, and the Spaniard is hoping his friend makes a swift recovery.
He told Sky Sports ahead of City's match against Huddersfield Town: "Brian Kidd, who is here now, was with [Ferguson] for a lot of time [at United].
"So a big hug and our thoughts are with his wife Cathy and the Manchester United family. I was glad to have dinner with him two weeks ago, and hopefully he can recover as quickly as possible."
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There had been no updates from United or from Salford Royal, where Ferguson was admitted, by 1.30pm on Sunday afternoon.
The club said on Saturday night that the surgery had gone "very well" but that Ferguson would need a period of intensive care to aid his recovery.
Ferguson had appeared fit and well when he presented his old sparring partner Arsene Wenger with a memento at Old Trafford last Sunday ahead of the Frenchman's departure from Arsenal.
But rumours began to circulate about the 76-year-old's health after Doncaster manager Darren Ferguson, Alex's son, did not attend his side's final match of the League One season against Wigan Athletic because of what was reported as a "severe family issue".
The Football Association, Premier League, Fifa, Uefa and individual clubs from Britain and around the world tweeted their best wishes along with a host of current and former United players.
Manchester United forward Jesse Lingard said: "Thoughts and prayers sir alex," left-back Luke Shaw tweeted: "Sending my love and best wishes to sir Alex," while former goalkeeper Peter Schmeichel wrote: "Please Be strong Win this one."
In their statement, the club added: "His family request privacy in this matter. Everyone at Manchester United sends our very best wishes."