Although the Manchester United boss declared on Tuesday that Rooney could be out for three weeks with the ankle injury he aggravated at Bolton last weekend, Ferguson has now revealed his star striker returned to training yesterday.
As usual, Rooney is pestering his manager to play in United's Premier League clash with Sunderland at the Stadium of Light.
Ferguson has no intention of agreeing in an attempt to save the 24-year-old from himself and ensure he starts to do himself justice again.
But with England not due in action until their October Euro 2012 qualifier with Montenegro at Wembley, Ferguson is willing to hand Rooney over to Capello and trust the Italian's judgement.
"It is really up to Fabio," Ferguson told Key 103. "You are talking about an extra 10 days. By that time, we would hope he will definitely be 100%.
"Wayne wants to play but now we have identified the injury, we have to be dead sure we are doing the right thing for him because he has not been doing himself the proper justice."
Not that Ferguson is condemning Rooney for his desperation to get involved.
Having scored just once this season - from the penalty spot - and been substituted after an hour at Bolton, many players would be happy to take a break from the limelight.
Rooney has never taken that attitude. But Ferguson feels the game has changed from the one where players could go into matches some way below their best.
"The problem with the lad is that he is too willing to play with injuries," said Ferguson.
"It is a great trait to have in any footballer. I have had many players over the years who might have had injuries but weren't prepared to miss a game because of them.
"But with the speed and number of games you have these days, fitness levels are really important."
Rooney is not the only fitness issue Ferguson is having to contend with.
Slightly less clear-cut with Sunderland in mind is the availability of Rio Ferdinand, Michael Carrick and Anderson, who all started Wednesday's win in Valencia after extended periods on the sidelines.
"We are going to check them," revealed Ferguson.
"Wednesday was Rio's first real game for six months. I know he played against Rangers and Scunthorpe. But that was a real game on Wednesday and you have to go back to April since he was playing consistently.
"Michael Carrick played in the Community Shield but he had been bothered by his Achilles and Anderson had only played one game since injuring his cruciate ligaments at West Ham."
Not that Ferguson has too many choices as, like Rooney, veteran duo Ryan Giggs and Paul Scholes are not being considered this weekend after missing the trip to Spain with hamstring and calf problems respectively.
The one area where United do have plenty of depth is amongst their strikers, which is possibly why Ferguson is so relaxed about Rooney.
Javier Hernandez was the midweek matchwinner, coming off the bench to score the only goal at the Mestalla Stadium.
Dimitar Berbatov is topping the scoring charts with seven, while Federico Macheda has looked lively on his recent appearances.
Then there is Michael Owen, who scored three goals in a week but did not have any involvement against Valencia.
"It is difficult with the strikers at the moment," agreed Ferguson.
"They all have their qualities and Michael Owen would be disappointed he didn't take part on Wednesday because of his recent contribution.
"But he is a really good footballer and has been training very well.
"He has scored three goals already and will be involved in a lot of things."