LIONEL MESSI v ALVARO ARBELOA

The little Argentinian maestro was forced to sit out Barca's stirring display against Inter Milan in midweek, but has now rejoined normal training with the squad. Though coming back from injury, this footballing genius cannot be given an inch of space, or he will undoubtedly punish the Real defence. With Barcelona playing at home, the Camp Nou expects great things and they surely won't be disappointed.

Arbeloa's versatility is a gift and a curse and he has been charged with the task of looking after Messi by reverting from right-back to left-back. Of all the key battles, this must be the least evenly weighted, as many will extol the virtues of Messi but hardly rant and rave about the ex-Liverpool defender's quality.

XAVI v LASSANA DIARRA

An intriguing battle will commence in midfield between the creator and the destroyer, in a battle that is surely the most crucial to the eventual outcome of the game. Xavi was superb against Inter in midweek, and one expects he will continue his good form against Los Merengues. So often, it is Xavi who is the key to all of Barca's forward play, and anyone would find him difficult to handle, but Real have one of the best solutions possible to deal with him.

Since Diarra - or 'Lass' as he's known in Spain - moved form Portsmouth to Real, he has assumed the role of a Claude Makelele-type player, who breaks play up and is just as important to Real's team as Kaka, Cristiano Ronaldo and Karim Benzema. When Makelele was sold by Real, their dominance began to wane, and with the current team's addition of Diarra, Real have a solid sweeper once again. Just how far he has come since his Fratton Park days will be surely be tested on Sunday against La Liga's most effective playmaker.

DANIEL ALVES v CRISTIANO RONALDO

Ronaldo's pace, goals and dead ball ability is second to none, and he has earned the title of best in the world. But he has just returned from an ankle injury, and though it is unthinkable for Real coach Manuel Pellegrini not to play him, he may not be at his most effective.

With Ronaldo getting most of his joy this season by cutting in from the left, Daniel Alves the Barca right-back will have his hands full; not least because he likes to push forward himself, leaving space for Ronaldo to exploit. But Alves is a savvy and pacey defender, who is just as adept as Ronaldo at judging when to take a fall. Though there may be plenty of tumbling over on Sunday, there will also be some great football emanating from these two.