Brian Kidd: Sir Alex Ferguson was unreal for Manchester United

Alex Ferguson won his final Premier League title with Manchester United in 2013

I was hoping it wasn't true.

Souness, speaking on Sky Sports said 'The entire world of football will be wishing him well.

McGrath, who played under Ferguson between 1986 and 1989, posted a picture of himself with his former boss to Instagram. All my thoughts and prayers are with him and his family. "Be strong boss", he wrote on Twitter.

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. Our thoughts were only with Sir Alex and his family.

There was a heartfelt message from former United goalkeeper Edwin van der Sar and his wife Annemarie, who herself recovered from a brain haemorrhage in 2009.

After defeat to Chelsea, Klopp said: "I met Sir Alex after the first leg against Roma, he passed my way together with Gerard Houllier".

"Cristiano Ronaldo, who bloomed into one of the finest players of all time under Ferguson, lead the messages of well wishing by urging the 76-year-old to 'be strong".

Midfielder Michael Carrick said he was "absolutely devastated", adding, "All my thoughts and prayers are with him and his family".

The sympathy extended beyond those with United connections, with Vincent Kompany, the captain of recently crowned English champions Manchester City, summing up the mood of many messages from rival clubs when he said: "Hang in there Sir Alex. Thoughts are with the family and close ones".

Several football clubs such as Manchester City, Leicester City, AC Milan and Al Ahly SC wished Ferguson a full and quick recovery after the surgery.

Ferguson's only real significant career regret was he managed to win the Champions League only double, however, also the first triumph was part of the 1999 treble that additionally included the Premier League and FA Cup.

Fergie and Arsene were bitter touchline rivals in the 1990s but the pair embraced before the Frenchman's last visit to Old Trafford as Arsenal manager eight days ago before he leaves the London club after 22 years at the end of the season.

It was reported that Ferguson's wife and his three sons remain at his hospital bedside after he was put into an induced coma following the surgery.

The most successful manager in British soccer history, Ferguson has appeared in good health since ending his intense direct involvement in coaching.

Ferguson can claim to have done it all, from winning in Europe with an unfashionable smaller club, lifting league titles in two different countries, collecting European silverware with two clubs and annexing trophies in four successive decades.