Sir Alex Ferguson put his bravest face on yesterday and did his best to pretend all was normal but he will also be painfully aware that growing numbers of Manchester United's supporters appear to have lost faith in him. At a time when Ferguson is at one of his lowest ebbs he might have hoped for sympathy and understanding but instead there was scathing criticism and the stark realisation that the abuse levelled at him after Saturday's defeat by Blackburn Rovers will not be a one-off if results continue to go badly.

Ferguson seemed in denial, refusing to answer some relatively trivial questions before tonight's Champions League Group D tie against Benfica. When the probing continued and he was asked for his reaction to being booed by United's own supporters, he abruptly ended the briefing.

By then he had refused to be drawn on his abandonment of United's 4-4-2 system and the acrimonious fall-out of Saturday's game, when supporters booed him down the tunnel. This is a period when Ferguson might benefit from providing some candid answers, explaining why he believes the 4-3-2-1 system to be workable, why he omitted Wayne Rooney from the Blackburn game and how he intends to close the gap on Chelsea. Instead he evaded the burning issues, a decision that has exacerbated the irritation of many United fans.

"What happened on Saturday was a build-up of ill feeling that has gone on for a long time," Johnny Flacks, the founding member of the Independent Manchester United Supporters' Association (Imusa), said last night. "The supporters have been accustomed to mediocrity for too long and this was the moment when they decided that enough was enough. You can argue whether it was good, bad or indifferent to boo the manager but what other option do supporters have to show their displeasure?

"The level of discontent at Old Trafford has reached proportions that I never thought it would and the great pity is that Ferguson does not deserve this when you look at what he has achieved in the past.

"It's just a shame he didn't leave after we had won the treble in 1999 or when he initially said he would retire [in 2002] because ever since then there have been serious levels of underachievement. Over the last four years some of his signings have been so questionable that you have to wonder whether he has even seen these players before buying them.

"He also needs to realise that he has a duty to speak to the fans through every media outlet that is available to him rather than ignoring us and sending out his sidekick [Carlos] Queiroz, a man who is derided by the vast majority of Manchester United supporters and whose record at other clubs has been one of failure."

Queiroz is unlikely to have improved his standing by using the word "stupidity" in an interview with the Portuguese newspaper O Jogo when discussing the fans' clamour for a return to 4-4-2. "People have been crying out for us to use a 4-4-2 formation but in the Blackburn game we tried the system the fans have been demanding and we lost," he said. "That's why football is a game in which imagination and, on many occasions, stupidity has no limits."

The sense of despondency engulfing Old Trafford has certainly been noted by Benfica. "The name of Manchester United always makes an impression but they have shown that there is nothing to be scared of," said the Portuguese attacker Simao Sabrosa. "Old Trafford holds no fear for us. Edwin van der Sar is a better goalkeeper than they had before but they make so many errors in defence it does not matter.

"They are not at their best at the moment and it is a great opportunity for Benfica. United without [Roy] Keane, [Gabriel] Heinze, [Gary] Neville and [Wayne] Rooney is one that can be beaten."

Simao could have added Mikaël Silvestre, who is unlikely to have recovered from an injury sustained against Blackburn. John O'Shea also faces a late fitness test for a match Ferguson simply dare not lose.

How the big questions were avoided From the press conference . . .

Reporter: "Bearing in mind what happened on Saturday, has this been a particularly bad couple of days for yourself?"

Ferguson: "Listen, I'm not getting into anything about myself. I thought that had been made clear. This is about our game against Benfica."

R: "Are the two not related?"

F: "The Benfica game is important to me. We're doing a good job of getting our players ready."

R: "Why has it been such a disappointing September?"

F: "As I've said, I'm here to talk Benfica. It doesn't matter what's happened before."

R: "Will the reaction on Saturday inspire your players?"

F: "European nights are different anyway. There have been some great European nights here."

R: "What did you make of the booing on Saturday?"

F: "I'm not getting into that. That's it finished. Thank you."