Ronaldo left Old Trafford for a world record £80million in 2009 to pursue his long-held dream of playing for Real Madrid.

However, life in Spain so far has not turned out as Ronaldo would have hoped.

For the second season running Real are destined to finish runners-up to Barcelona in La Liga whilst Wednesday's controversial 2-0 defeat to their fiercest rivals at the Bernabeu means, almost certainly, it will be the Catalans who make it through to next month's Champions League final at Wembley.

As United have coped with Ronaldo's departure rather better and are well placed to regain the Premier League, in addition to facing Barcelona on May 28, there has been some talk the former world player of the year would be interested in a return to Old Trafford.

But Ferguson, who was in Madrid to watch Wednesday's stormy confrontation, does not see how that could happen.

"It would be very difficult," said Ferguson, when asked whether Ronaldo could come back.

"He had a great time here but he is at a great club now too."

Few connected with United have anything but good words to say about Ronaldo, who scored 118 goals in 292 appearances for the Red Devils, helping them to three championships on the trot and the 2008 Champions League.

Ferguson continues to think of him as the best player in the world, despite the competing claims of Lionel Messi, and wasted little time seeking Ronaldo out on Wednesday to commiserate at Real's demise.

"I spoke to him after the game," said the United chief.

"He had a great time here, we got six years out of him. We got him as a kid and he went to Madrid a man.

"He is enjoying being there and though he might not have been at his best on Wednesday, he is still a great player."

In fact, it could be argued Real's over-reliance on Ronaldo is one of their weaknesses.

As a team, they are clearly inferior to Barcelona and Ferguson accepts the only way to get the best from each individual is through the unit as a whole.

"Teams always win the big competitions," he said.

"Individuals can make a difference, as Ronaldo did many times for us, but if you look at the work-rate of our team collectively on Tuesday night that is what we try to aim for.

"If we achieve anything it will be the collective that does it."

United also try and aim for the entertaining brand of football they produced against Schalke on Tuesday, for which Barcelona are also noted.

However, no-one aspires to the kind of spectacle Barca were part of on Wednesday.

Aside from Messi's brilliant second goal, the game will be remembered for its spiteful edge, persistent play-acting and Jose Mourinho's outrageous comments at the end.

Ferguson is wisely staying out of the argument, although it did cross his mind on the night how little football was actually being played.

"This is not the time to discuss it because there is so much in the post-match analysis, with the recriminations on both sides," he said.

"We should let the dust settle and concentrate on reaching the final.

"The only thing I would say is that there could have been only one hour's play because the game stopped so much.

"You want to go to a game and see an hour and a half."