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In terms of talent, Real Madrid are clear favourites to overcome Manchester United: they have better players, who in turn come together to form a better team. All the betting points to a Madrid win (bookmakers are offering just 1.58 euros per euro bet), and general opinion would appear to agree.

True, when United are on song they begin to look something like Madrid: their strengths lie in excellent forwards and a clear inclination towards playing on the break. Yet there is little escaping that, even at their counter-attacking best, the Old Trafford side can only match a Real distinctly far from their best. And when it comes to weaknesses, the comparisons come to an end. Sir Alex Ferguson's men offer nothing out of the ordinary in creation and defensive solidity. It seems almost unthinkable that the visitors should leave the Santiago Bernabéu without shipping a few goals, nor that they should keep a clean sheet in the return leg. The prediction seems pretty clear, then: 'los blancos' in the quarter-finals.

Yet there is more to this fixture than meets the eye. Most significant, perhaps, is the importance the tie has for Real: it really is last-chance saloon to save their season. There can be no doubt that this will weigh upon the players' shoulders should things begin to turn against them. Maybe even if they don't. Just look at what happened against Bayern Munich last year: the team came out all guns blazing, before shrinking further and further back and meeting their fate on penalties.

If Madrid score the first goal, let nobody be surprised if coach José Mourinho puts men behind the ball and cedes possession to United. Theoretically, at least, it's an irreproachable tactic. However, we have seen a number of times now that dousing the flames of euphoria in favour of prudence does not sit well either with the team or the Bernabéu. This has been the case in two separate home Clásicos, not to mention the second leg of the last Supercopa: a quick 2-0 lead followed by retreat and a Barça siege (with ten men). A 2-1 win, but not a comfortable one.

The presence of Michael Essien in Tuesday's press conference suggests that Mourinho may exercise caution and include the Ghanaian in a 'trivote' of three holding midfielders (the Portuguese coach has commented before that "those who speak before the match are in the starting line-up"). It would seem to make sense. Xabi Alonso is not at full fitness and may need the support of Essien and Sami Khedira, while such a tactic would provide a counter-weight to the expected line of five - including a deeper Wayne Rooney - in United's midfield.

Some may ask (and they'd be right) why a match is turned into a tactical battle when the war could be won by letting the usual suspects win the war the way they usually do: through football, pure and simple. Others would respond (and they'd also be right) that this is an occasion incomparable with the home games Madrid are used to playing in La Liga - little more than domestic processions in the face of relative cannon fodder. Wednesday's game bears comparison only with the visits of Borussia Dortmund (2-2), Manchester City (3-2) and Barcelona (2-1), and in each case Madrid were caused problems and conceded goals.

As ever, Cristiano Ronaldo will provide the 'X factor'. He comes into the match in a rich vein of form, straining under the weight of goals and appreciation, and thrilled to face his mentor and former team-mates. The mission for Rooney and Robin van Persie is to match Cristiano between them; and if they do, the mission for Karim Benzema is to re-establish the imbalance.