Sir Alex Ferguson finds himself in the unaccustomed position of having to defend his record amid criticism from irate supporters.

He was booed after Saturday’s 2-1 home defeat by Blackburn Rovers, but rather than dwell on the supporters’ frustrations, Ferguson spoke of the lure of European football.

“We have a game against Benfica that atmosphere-wise, historically, is a fantastic game of football for our young players. There is an extra edge to a European game and it’s a challenge to every player because they are playing the best players in the world. It’s a bigger tournament than the World Cup now.”

Ferguson’s position is not helped by the glut of injuries which have hit the club since the start of the season.

Gary Neville, Gabriel Heinze and possibly John O’Shea – as well as Roy Keane are out through injury, while Wayne Rooney is suspended.

Even Benfica coach Koeman admitted: “They are not at their best.”

“We have more chance of getting a good result than if they had all their players or were in a very good moment with a lot of confidence.

“But it’s different from the league, it is the Champions League – they have enough qualities to produce a good reaction and we have to prepare for that. We know they will start aggressively to get an early goal so we need to be ready.”

Koeman will welcome back Greek international Georgios Karagounis from injury – potentially in place of Geovanni – and is looking forward to seeing pacey forwards like Simao and Fabrizio Miccoli test United’s understength defence.

“We can hurt them because we have quicker players in our attack than they have in their defence,” said the former Ajax coach.