As it turns out however, it is the depletion of United's defensive resources that represents the most significant element in the backdrop to Tuesday's semifinal first-leg at Old Trafford.

Already deprived of club captain Gary Neville and Nemanja Vidic, United must also do without Vidic's centre-back partner Rio Ferdinand as a result of the groin strain the England international suffered in Saturday's 1-1 draw with Middlesbrough.

Defensive solidity has provided the foundation for the revival of Sir Alex Ferguson's side this season and there is no doubt that he will regard the loss of both Vidic and Ferdinand just as the season reaches its climax as hugely unfortunate.

But although the Scot will readily admit that his squad has been reduced to the "bare bones", he refuses to accept that Milan, who have recently struck a rich vein of form, will start the semifinal tie as favourites.

"It's not a time for feeling sorry for ourselves. It's time to show what we are made of," Ferguson said. "It's been well documented in the history of our football club that we do it the hard way and we have to get the players' energy energies right for Tuesday, because it is a massive game for them and it's a game they should enjoy."

Ferguson's opposite number, Carlo Ancelotti, has admitted that a Ronaldo-inspired United have probably played the best football of any team in Europe this season.

But the Milan coach is also aware of how much United's recent injury setbacks have hurt Ferguson, describing the loss of Ferdinand as highly significant.

"He is a very important player for their defence," Ancelotti said before admitting that he is, in fact, more concerned about the attacking threat posed by Ronaldo, Wayne Rooney and Ryan Giggs.

"We will have to be careful and keep possession of the ball but that could be a two-edged sword, because if we do not do well our opponents could hit us on the counter-attack," Ancelotti said.

Milan emerged as comfortable winners when the two sides last met winning both legs 1-0 in the first knockout round of the tournament two years ago.

But United are a vastly improved side since then and Milan's cause has not been helped by the fact that Ancelotti is sweating on the availability of his first-choice goalkeeper, Dida.

If the Brazilian, who is struggling with a shoulder injury, does not make it, Milan will be forced to deploy giant Australian Zeljko Kalac, who has just played four Champions League matches compared to Dida's 60.

Ancelotti will leave it until the last minute before making a decision on Dida's fitness -- a stance that casts doubt on his stated belief that Kalac has "rediscovered his confidence" and is "ready to step in" to an environment as demanding as Old Trafford on Tuesday night.

The Milan coach got his hands on the Champions League trophy when his side beat Juventus in a penalty shoot-out at United-s fortress four years ago.

But he readily accepts that eliminating United represents a major challenge.

"They have great quality and they will look to exploit the pace of Ronaldo and Rooney. We will have to make the most of the ball when we are in possession. We have great respect for them, but we have no fear. We are in good shape."