“Sir Alex Ferguson has undergone emergency surgery today for a brain haemorrhage,” said a United statement.
“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.”
Ferguson’s son, Darren, the manager of English third tier club Doncaster, missed his side’s League One match against Wigan on Saturday.
“Darren Ferguson will not be at Saturday’s game due to family reasons,” said a Doncaster statement before kick-off.
“Darren asks for privacy, and will provide an update through the club during the week.”
The 76-year-old Alex Ferguson retired as the most successful manager in British football when he called time on his Manchester United career five years ago.
He was back at Old Trafford last week to present a commemorative vase to old rival Arsene Wenger, who steps down as Arsenal manager at the end of the season.
His more than 26 years in charge at Old Trafford saw Ferguson guide United to 13 Premier League titles, with the Scottish manager also leading the Red Devils to two European Champions League triumphs.
In 2003, Ferguson, who made his name as a manager with Scottish club Aberdeen, was treated in hospital for a heart irregularity.
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