Sir Alex Ferguson has raised a question mark over Rio Ferdinand's ability to star at Euro 2012 by claiming it would be impossible for the defender to play two matches in the space of four days.

The Manchester United boss was actually explaining why he had written to the Football Association stating that none of his over-age players, with the exception of Ryan Giggs, would be available for selection for the Great Britain Olympic squad this summer.

However, as England could end up facing a schedule of six matches in 21 days, just four days more than the one Stuart Pearce's GB outfit will be plotting for, the same fears over Ferdinand's fitness appear to apply.

"In the Olympics you play something like a game every four days. Rio Ferdinand couldn't do that," Ferguson told MUTV.

With Roy Hodgson set to name his European Championships squad on Wednesday, Ferguson's words provide him with a new dilemma to ponder.

Thus far, Hodgson is yet to speak with Ferdinand and deposed skipper John Terry about their willingness to play alongside each other, with speculation intensifying in recent days that the Manchester United man was more likely to be selected.

However, if Ferguson's words are to be taken at face value, Hodgson may be deciding whether he can afford to take a risk with Ferdinand's fitness, as Fabio Capello did with Ledley King at the World Cup, only for the move to backfire when the Tottenham man's troublesome knees gave way.

Ferdinand's situation is a side issue for Ferguson, who has confirmed that fellow defender Jonny Evans requires an ankle operation that rules him out of Olympic duty, while he is also pondering groin surgery for Chris Smalling, which could also cost him his place after already being ruled out of Euro 2012.

One player Ferguson would be happy to release for the Olympics is Giggs, whose willingness to play may yet meet opposition from the Welsh FA.

"Ryan wants to play. I am happy with that. He is looking forward to it.

"Whether he plays three games in seven days is another matter - that is not my decision.

"But he does want to play because he has always missed out on the big tournaments with Wales."

It would not be too wild to speculate Ferguson has had a slightly harder task persuading Javier Hernandez not to play for Mexico.

However, after successive tournaments - World Cup and Gold Cup - during the summer, the United boss feels it is time the striker had a break.

"Mexico have five games in the summer," said Ferguson.

"After you have played a full season in England, five more games is a big task.

"We are trying to cut that down a bit.

"Mexico is a very patriotic country and all their players are patriotic. Javier wants to play.

"But we want him to get some proper rest."