Ferguson stunned the travelling Red Devils support in the Stadio delle Alpi by opting to drop Keane into defence alongside Rio Ferdinand against Juventus, even though he could have played John O’Shea in the same position and moved Phil Neville to full-back.

However, any doubts over the Irishman’s suitability for the role were quickly dispelled as he turned in a superb display as United cruised to their memorable 3-0 triumph.

By his own admission, the rigours of injury – in particular his troublesome hip – have inhibited Keane’s all-action style, leaving some pundits to suggest that the defensive duties may become more permanent.

Ferguson has admitted it is an option open to him but Keane is not believed to be in favour and the return of Mikael Silvestre for Sunday’s clash will ensure United’s influential leader can step back into the midfield holding role he has earmarked for the current stage of his career.

“It took Roy about 15 minutes to settle into Tuesday’s game but once he started to make sure he could see his opponent, he grasped the role very quickly,” he said.

“In the end, he could have played with a bowler hat and white gloves on it was so easy for him.

“He is a marvellous player and choosing him in defence is certainly an option but Mikael Silvestre and John O’Shea should be fit and I have a back four in my mind.”

Ferguson also has not given up on Wes Brown making the game, although the England centre-half is extremely doubtful after suffering a hamstring injury in last Saturday’s Premiership draw at Bolton.

The thigh injury Ryan Giggs picked up against Juve looks set to rule the Cardiff-born winger out of an emotional return to his home city, although Ferguson is more optimistic about Paul Scholes’ chances of overcoming the groin strain which has ruled him out of the last two games.

If Giggs doesn’t make it, Ferguson will probably end up with a choice between Nicky Butt and Ole Gunnar Solskjaer for the final starting slot, with Juan Sebastian Veron either starting alongside Keane or wide on the left depending on which way the decision goes.

Even for a notoriously hard man like Ferguson, informing his squad of the final outcome presents a tough challenge, although one he will not shirk as Jim Leighton will testify after his brutal axing for the FA Cup final replay against Crystal Palace 13 years ago.

“The injuries might spare me the horrible part of this job because telling someone they are not playing in a final is the hardest thing you can do,” said the United boss.

“It is sod’s law that Ryan got injured on Tuesday because I didn’t want to use him for more than half an hour.

“He was carrying a calf injury and sometimes you don’t know if that is the reason something else goes. We will give him every chance because he will be desperate to play in Cardiff but he is very doubtful.

“In the course of a full season, you are bound to get injuries but when they mean you will miss a final, it is obviously going to hurt them more deeply.”

Ferguson made the short journey to Anfield last night to watch Liverpool squeeze past Auxerre and book an eye-catching UEFA Cup quarter-final with Celtic last night.

And, while his side will start favourites to land the League Cup for only their second time in their history, the Scot will be acutely aware of Liverpool’s impressive recent record against his team.

The Anfield outfit won the only previous Millennium Stadium clash between the teams – last season’s Charity Shield – and were on a run of five successive wins until Diego Forlan’s double saw the Red Devils triumph on Merseyside in this term’s only Premiership clash to date.

“It was important to stop that run of victories and hopefully we can win a few ourselves now,” said Ferguson.

“It is four years since we last got to a final, which is a long time for this club.

“We have players who have not been involved in a final before and it will be a fantastic experience for them. Even though they are used to playing in front of big crowds in the Premier League and Champions League, this will be something different and it won’t do them any harm.

“If you look through the squads of both teams, there is plenty of quality, so there is no reason why we can’t have a great final.”