Stapleton pointed out that United had sold star players in the past and had not suffered when David Beckham and Jaap Stam left the club, or when Eric Cantona retired.

Stapleton said: "I feel that money will be used very, very quickly.

"The Champions League final for Sir Alex Ferguson will have opened his eyes, what Man United need to do to stay top, not only in England but in Europe."

Manchester City manager Mark Hughes is adamant Ferguson is only letting Ronaldo leave United because he believes it is in the best interests of the Old Trafford club.

"There seems to have been a lot of speculation about Ronaldo's future for a number of seasons, to the extent it has started to become predictable," said Hughes.

"Obviously Manchester United feel it is good business for them.

"Sir Alex Ferguson makes key decisions very quickly and I suspect he will have been very much involved in what has happened.

"He has made what he thinks is the right decision for the club and we have to respect that."

Former United full-back Arthur Albiston believes Ronaldo's exit could lead to Carlos Tevez remaining at Old Trafford next season.

Albiston, who made 485 appearances for United, said: "Cristiano might end up staying but I very much doubt it.

"Once the club have given him permission to speak to Real Madrid, I think that will be it and he will be on his way.

"It (the news) has not come as a great shock. There were a lot of rumours last season about him leaving.

"You do not want to hold on to a player who is not going to show total commitment to the club.

"Having said that, he has been a fantastic ambassador for the club. United have had six years out of him; supporters probably do not realise that as he is so young.

"I don't think they can turn it (the transfer fee) down. The only problem the manager has got is to find someone to replace Cristiano given the number of goals he has scored.

"When (Ruud) van Nistelrooy left, people said the manager did not know what he is doing but Ronaldo stepped up to the plate."