Sam Wallace: United midfield will be key to the summit meeting

What will the old devil do this time? Twenty years on and still Sir Alex Ferguson is obliged to come up with yet another solution to the threat facing Manchester United's great tradition. Another must-win game to go with all the others down the years he was told he could not lose. Another piece of ingenuity required to convince his players that their professional lives are dependent on this given Sunday afternoon.

When Chelsea's chief executive, Peter Kenyon, was modestly laying down his plans for global domination at Stamford Bridge on Thursday, talk strayed into keeping Jose Mourinho and then on to Kenyon's role in Ferguson's decision to postpone retirement in January 2002. It might have been the only thing Kenyon said that day with which Ferguson would have agreed. "Football is in Alex's veins," Kenyon said, "and I think he realised that without football there wasn't a lot else."

There is a certain bleakness to that assessment - a bleakness that Ferguson the grandfather, the wine connoisseur, the biography fanatic might dispute - but when Old Trafford's great dictator walks down the touchline tomorrow to take his place in the dugout, it will make a lot of sense. What else is there apart from this? The challenge is vast and thrilling, putting his great reputation - eight Premiership titles - on the line to win one, maybe two, more. Chelsea plan to take over the world by 2014, Ferguson wants to have done it by the end of May.

Beating Mourinho's Chelsea of 2006-07 - a problem like no other. How to beat a football team that does not look like a football team should? A midfield bereft of wingers and filled instead with international muscle, four awe-inspiring athletes in Michael Essien, Michael Ballack, Frank Lampard and Claude Makelele who see no reason to beat their opposition down the flanks. Not when they can rampage through the middle. Which is why so many teams find themselves inhibited when confronted with the heavy mob - and change accordingly.

So the question facing Ferguson goes right to the very heart of the kind of team United are - or at least aspire to be: 4-5-1 or 4-4-2? Play a five-man midfield and the unsaid acknowledgment is that this United team cannot beat Chelsea's midfield quartet man-for-man. It may only be November, and the gap between United and the champions in second a slender three points, but it is surely no time to be playing for a draw at home to Chelsea.

Who makes this decision? The father of 4-5-1 in its various guises at United over the last two years has consistently been identified as Carlos Queiroz, Ferguson's Portuguese assistant, the inauspicious touchline prowler who looks more like an affable airline pilot than the man dictating tactics at the country's most famous club. You could see why Ferguson brought him in four years ago, and then welcomed him back after a season at Real Madrid. Queiroz delivered Cristiano Ronaldo, he looks the type to make United more literate in European football's subtleties and, goodness knows, Portuguese coaches are in vogue.

The relationship of Ferguson and Queiroz, however, is the real mystery of English football. We agonise over Rafael Benitez's inscrutability and the detachment of Arsène Wenger but little more than nothing is known about a man who is so central to the latest phase of the Ferguson dynasty, or how he earned the trust of such a complex football man. Does the old general feel that he needs, 20 years on, a younger, more modern approach to the business of winning football matches? It would be a shame if that came tomorrow at the cost of United's more expansive, attacking style. Even the most ardent zealot of cautious football would have admitted that, on Tuesday night, Celtic were ripe to be beaten in the first half while United had Louis Saha alone in attack struggling to make something meaningful from their endless possession. And when 4-5-1 comes at the cost of Wayne Rooney on the left wing, it seems too high a price to bear.

This new Mourinho team appears fortified, reinforced for a third summer against the possibility of losing football matches. There are still minor areas of weakness, most noticeably at right-back where Paulo Ferreira is out of favour, Geremi has improvised recently and Khalid Boulahrouz has said he does not wish to play.

It was Ronaldo who Boulahrouz mowed down on his way to a red card at the World Cup, a studding that looked more like a gunshot wound, and it is an obvious area of tension between the two sides. There are other reputations at stake, too, most obviously Andrei Shevchenko who has been so completely overshadowed by Didier Drogba that his failure to score consistently has been much less of an issue than it otherwise might have been. How long does Mourinho persist with him?

And there is Michael Carrick whose star has risen lately but who conspicuously failed to take the game in hand against Celtic on Tuesday. Is he a player for a moment of crisis, for the time his team are pushed up against a cold wall? And more importantly, can he ever be United's Lampard - a player with an all-conquering self-belief? If Carrick really is a big game footballer then this would be the ideal game to start embracing the idea.

On Thursday, Kenyon spoke in awed tones about "the owner" as if even naming Roman Abramovich is now an affront to the dignity of Chelsea's ruling junta. At United they talk reverentially about "the family" when it comes to the Glazers. Everyone, these days, answers to someone. What does not alter are matches like these, when one manager's decision can galvanise a team, sway a game, change a season.

Mourinho on Ferguson:

'Maybe when I turn 60 and have been managing in the same league for 20 years and have the respect of everybody I will have the power to speak to people and make them tremble a little bit'

'He is a winner and has a history of winning. We have little words, little fights in the press, like when it was Porto against Man United or after the Carling Cup game. We can have a fight, but he is pure and honest. Five minutes later it is over'

Ferguson on Mourinho:

'He was certainly full of it, calling me Boss and Big Man when we had our post-match drink. But it would help if his greetings were accompanied by a decent glass of wine. What he gave me was paint-stripper'

'That youthfulness, that great optimism you have as a young person. You can't see danger. Sometimes with Jose Mourinho I think of myself as a young man'