Sergio Aguero first in line as Manchester United look to life after Cristiano Ronaldo

Sir Alex Ferguson wished Cristiano Ronaldo well yesterday as the former Manchester United star's record-breaking £80million move to Real Madrid was completed.

"Cristiano has been a marvellous player for Manchester United," said Ferguson. "His six years at Old Trafford have seen him develop into the best footballer in the world.

"His contribution has been a major factor in the club's success in that time and his talent, his ability to entertain and his infectious personality enthralled fans the world over.

"Everyone here wishes him well in his future career."

But the United manager must have uttered the eulogy through gritted teeth as Ronaldo has left him the seemingly impossible problem of finding a replacement.

He plundered 67 goals in his final two seasons at United, as he almost singlehandedly hauled them to Premier League and Champions League glory, before deciding to quit for Spain.

And although United have received the £80m fee in one go, an unprecedented situation in modern football, that has not made it any easier for Fergie to fill the void.

Antonio Valencia has arrived from Wigan for £17m but he is nowhere near as prolific as Ronaldo and cannot be considered a like-for-like replacement.

Lyon and France striker Karim Benzema, a long-term target for Fergie, last night joined Ronaldo at Real Madrid in a £30m deal.

And he looks to have missed out on another target with Valencia and Spain striker David Villa preferring to stay in La Liga at Barcelona.

The United boss is pressing ahead with his interest in Atletico Madrid playmaker Sergio 'Kun' Aguero, who is likely to cost £40m.

Aguero has the goal threat and star quality to replace Ronaldo, but Fergie faces a battle to persuade Atletico to part with their prize asset. (Read our Sergio Aguero profile )

With the start of the new season less than seven weeks away and United leaving for their preseason tour of the Far East in 13 days, the pressure is on to bring in new faces.

Fergie has told United chief executive David Gill that, ideally, he wants to have Ronaldo's replacement signed by July 15. But that looks unlikely as the targets Fergie has identified have snubbed United in favour of a move to La Liga with Madrid or Barcelona.

And the same looks set to happen with another United target, Bayern Munich midfielder Franck Ribery, who is also poised to join Real in a deal worth £50m in a year's time.

TOUGH TARGETS FOR FERGUSON

YES Antonio Valencia Joined from Wigan for £17m

NO Karim Benzema Joined Real Madrid for £30m

NO David Villa Set to join Barcelona

MAYBE Sergio Aguero United are still waiting

NO Franck Ribery Set to join Real Madrid

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