Ferguson was at Old Trafford last Sunday when he presented departing Arsenal boss Wenger with a commemorative trophy.
But on Saturday, the former United manager would have to undergo emergency surgery following a brain hemorrhage.
In their statement, the club added: "His family request privacy in this matter". We are united in our wish to see him make a comfortable, speedy recovery.
Ferguson's former club Rangers FC tweeted: "Everyone at #RangersFC sends their best wishes to Sir Alex Ferguson following emergency surgery". "Sending prayers and love to (wife) Cathy and the whole family". "Be strong, Boss!" the Real Madrid forward said on his Instagram account as he shared a picture of him and Ferguson during their time together at Old Trafford. Manchester United then confirmed the unfortunate news about their former boss.
Ferguson, 76, retired in 2013 as the most successful manager in British soccer history.
"Sir Alex I'm praying you get through this, you've won everything in life any player or manager dreams of, I as a friend am stunned.", England great Paul Gascoigne said. "Thoughts are with the family and close ones". "I hope he has a full recovery".
"Every brain injury is unique, as is every individual's recovery", he added.
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As well as being uppermost in the thoughts of our own players, past and present, Sir Alex has been the subject of many warm and touching comments from other clubs, governing bodies and individuals in the handsome game.
Everyone was shocked when the news came out and everyone is still hoping the United icon will be able to pull through by showing the fighting spirit everyone has associated with him once more.
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.
"No updates, just an endless list of tweets from the 4 corners of the world showing support and love".
Italian Serie A sides AC Milan and Inter Milan, Spanish LaLiga champions Barcelona and Scottish title winners Celtic were among a host of other football clubs, along with the National Basketball Association, to send get-well-soon tweets.