A dedicated few had taken the afternoon off to make their preparations for the visit of Barcelona this evening. At the Stretford End they were painstakingly laying out a shiny, silver paper replica of the European Cup, piece by piece across the seats, guarded on each side by the dates '68 and '99 in vibrant red. Opposite was a single gigantic word: believe.

The message was echoed by Sir Alex Ferguson, the Manchester United manager, who was working hard to shift to the back of his mind uncomfortable memories of last season's humbling by AC Milan, his third semi-final defeat, and a surprisingly poor Champions League record in home second-leg ties, when following up on a goalless draw away.

“A lot of things worry me about this match, to be honest,” he said. “It's a well balanced game and it will be more open than it was at the Nou Camp. It could go either way. I look at this one and create all sorts of images about how it could go.”

Not exactly a clarion call of defiance from the great man but, despite setting a Champions League record this season for successive home wins, little about United's recent form would justify blasé overconfidence, not least the one point from a possible six that has allowed Chelsea equal billing in the Premier League title race.

Even the stalemate in Barcelona came with a sting in the tail, considering that the same result against Monaco, Real Madrid and Rotor Volgograd in European competition under Ferguson ended in elimination. The most unsettling feeling about tonight's match is that the first leg result was as much to Barcelona's liking as United's, and may have been part of a grand plan, a modern way of approaching these knockout matches, to combat the advantage to the team playing at home in the second leg.

The idea is to play the first leg like the second leg, and vice versa. To make keeping a clean sheet the priority in the first game at home, stopping the scoring of the crucial away goal, and then playing the away match with increased dynamism, knowing that there will be bigger defensive gaps to exploit and that any goal scored will count double.

For all Manchester United's caution at the Nou Camp, there were two defensive sides on the pitch that night, and Frank Rijkaard's Barcelona were hardly guilty of playing with abandon. Tonight may be different. For a start, Barcelona have to score to progress without the aid of a penalty shoot-out; secondly, the onus on United as the home team to attack makes them vulnerable, particularly with Nemanja Vidic, their commanding central defender, being hurried back into the team, after suffering a facial injury against Chelsea.

“If we play like this is the final, we will reach the final,” said Txiki Begiristain, Barcelona's sporting director, even though Rijkaard, the coach, sounded a note of caution. “A game like this can be decided by details,” he said. “It is important that we keep our shape, because one goal might be the difference. We need to score that goal, so we must be brave, keep possession, pass it around, and dictate our style of play, rather than get involved in what Manchester United want us to do. On a scale of one to five, my optimism that we will win is five.”

Ferguson is convinced that Barcelona's style will not change, and on that he is certainly right, but the extent of their ambition may be heightened and United must be prepared to take on a team with considerably more urgency than was displayed last week. At first, Ferguson appeared almost dismissive of their potential, but contained in the appraisal of his opponents was a lovely lyrical phrase to describe the way Barcelona move the ball to mesmerise opponents: the passing carousel, he called it. And, this time, he must hope that it is not his players that are taken for a ride, as famously happened against the similarly gifted Real Madrid in 2000.

“I've watched Barcelona many times and always enjoy it,” Ferguson said, “but it is the same all the time: they play their football and they won't change, they can't change. It is always the same system. They try to get you on that passing carousel, try to make you dizzy, and you have to be patient. They are what they are, and we are not short of knowledge about them, but I still think I've called it correctly.

“We are going into the game with a marvellous chance and we have the players to win it, big-game players who can decide matches. It will be an open, balanced, fascinating match, tactical at times but with the type of explosions of play that we expect from our team. If you go back to semi-finals in the past, we were unlucky against Borussia Dortmund and Bayer Leverkusen and had we been fresher against AC Milan we would have done better.

“I thought our performance in the first leg last week was probably our poorest in Europe and that is a worry because I look for reasons why our attacking skills deserted us. We won't make the same mistakes again. I know we can play better, and we will play better. Time after time I have said this club should have had more success in Europe.”

In that respect, United and Barcelona could almost be twins. For two clubs, of such stature, with alumni that read like a who's who of world football and a reputation for flirting with sport as art, to have only four European Cup victories between them represents almost half a century of underachievement on a grand scale. There have been numerous years when either United or Barcelona have been regarded as the best team in Europe, yet came up short. This could be another one, if United are not crowned champions in Moscow.

Manchester United are holders of the record for the most consecutive home wins in the Champions League, a run that is still going and will stretch to 12 if they defeat Barcelona, yet Ferguson was dismissive of its worth when placed in context of success in the matches that matter.

He knows what is important. In time, all that is remembered is the name on the trophy. This year, that name should be Manchester United. Anything less and Ferguson will believe he has failed.