Roma win was one-off - Ferguson

After dismantling one major foe from Serie A, United meet a true Italian giant in the Champions League semi-finals, but the hosts' chances of success have been badly affected by injury with all of Ferguson's first-choice defenders ruled out, plus Park Ji-sung and Louis Saha.

"It is difficult to think we can get to that standard," said the Scot. "That was a once-in-a-lifetime result. But, with the players we have, we should still expect a very good performance."

He added: "The players want to reach a high level because of the quality of our opponents. The importance of the occasion demands the best performance to get us through.

"It is not going to be easy but it is never going to be that in the semi-final of this competition."

With so many defenders out, the emphasis will be on United's superb array of attacking players to get the result required.

Cristiano Ronaldo and Paul Scholes - first and third in the PFA Player of the Year awards on Sunday - plus Wayne Rooney and Ryan Giggs, will carry United's major threat. And it is a man Ferguson knows well, Gennaro Gattuso, who will attempt to stop them.

The United boss has followed Gattuso's career with interest since he spent a year at Rangers and the combative World Cup winner went so far as to claim Ferguson tried to buy him when he was at Sampdoria.

"He is a player we have always admired," said Ferguson. "He is an excellent footballer who has matured really well at Milan in the last two years.

"When he was younger he was more aggressive. He still has that Glasgow narkiness but he is also far more mature in his game."