The 76-year-old footballing legend appears to have survived the devastating brain attack, but medical experts say the 48 hours after the operation are crucial.
Sir Alex, who managed United between 1986 and 2013, remains in intensive care at Salford Royal Hospital following surgery on Saturday, having been taken there after falling ill at home.
Television presenter Eamonn Holmes, a longtime friend of the football hero and Manchester United fan, described him as an "amazing man".
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The Arizona Republic reports the pop star showed up unannounced Saturday at the Arizona Burn Center to see Isabella McCune. The note stated that Taylor hopes Isabella feels better soon and that she was honored she has been listening to her music.
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 met Sir Alex after the first leg against Roma". Everyone thinks it was all this "hairdryer", but the boss enjoys a good time, really enjoys his racing and is good company when you're around him.
David Beckham, who was signed up by Sir Alex as a schoolboy, led the well-wishers, writing on Instagram: "Keep fighting Boss".
Ferguson underwent emergency surgery for a subarachnoid brain haemorrhage last night.
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The KTTA has also proposed a unified Korean team at this year's Asian Games in Indonesia, pending the ITTF's approval. I feel a little bit unusual that I'm in the united team now.
It shared a number of messages sent from footballing bodies, including Federation Internationale de Football Association and UEFA, as well as clubs from across the globe. He's a colossus of the game; of the British game and the world game.
Van der Sar who was United'a goalkeeper when Annemarie, suffered a brain haemorrhage in 2009 from which she has since recovered. "In some cases, extensive rehabilitation is needed to regain function, including speech therapy and physical therapy".
The procedure is said to have gone very well, with Sir Alex needing a period of intensive care to optimise his recovery.
Premier League executive chairman Richard Scudamore: "It's obviously a big shock but the most important thing is to wish him well, and his family well, to respect their privacy, and hope that very, very soon he's back to his best".
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It's some lovely news following February's tragedies when Jordin lost four loved ones in one week, including her step sister . Jordin added that although feeling great she wanted to ensure she remained careful so she didn't end up back in the hospital.