Manchester United have thanked the football world for its support as Sir Alex Ferguson remains in hospital after suffering a brain haemorrhage.
The 76-year-old, one of the most successful football managers of all time, had surgery on Saturday and is in intensive care.
Arsenal manager Arsene Wenger was among the latest to send his best wishes to his old rival - and one of the game's greats - Sir Alex.
There was no further update on his condition on Sunday evening, although his former club Manchester United thanked the football community for its expressions of concern.
The post said: "Manchester United would like to thank the wider football world for the messages of support following the news that Sir Alex Ferguson underwent emergency surgery on Saturday evening."
Meanwhile, Wenger, who was presented with a memento to mark his impending departure from Arsenal by Sir Alex last weekend, said the Scot is "a strong man and an optimistic man".
Speaking on the pitch after his final home match in charge of the Gunners, he said: "I was with him on the pitch last week, I went to see him in the box after the game on Sunday. One week later, he looked in perfect shape.
"He told me he's doing a lot of exercise, he looked very happy, but that kind of accident can happen.
"We wish him very well and that he recovers very, very quickly. He's a strong man and an optimistic man. I got calls last night from Manchester and nobody knew exactly what it is."
Sir Alex's operation went "very well", Manchester United said on Saturday.
When it emerged Sir Alex was in hospital, football fans - including names from the worlds of sport, politics and television - set allegiances aside to unite in sending their best wishes to one the game's greats.
In a statement on Saturday, Manchester United said: "Sir Alex Ferguson has undergone surgery today for a brain haemorrhage.
"The procedure has gone very well but he needs a period of intensive care to aid his recovery. His family request privacy in this matter.
"Everyone at Manchester United sends our very best wishes."
Sir Alex retired in 2013 as one of the most successful football managers of all time when he made the bombshell announcement he was leaving after 26 years at the helm of the Old Trafford club.
During that time, he took the club to the pinnacle of the English and European game and the decision saw United's shares go down 5% on the New York Stock Exchange amid worries over whether the club could find the right replacement.
With his uncompromising "hairdryer treatment" style of management, he led United to 13 Premier League titles, two Champions League crowns, five FA Cups and four League Cups.
He also won the treble of Premier League, FA Cup and Champions League in 1999, the year in which he was knighted.
Born into a family of shipyard workers in the Govan area of Glasgow, Sir Alex has been a well-known Labour supporter and has been named in the past as one of the party's biggest donors.