Arsenal v Barcelona

Arsenal will need to be at their scintillating best if they are to take a vital lead to Barcelona. Memories of Paris in 2006 will inevitably be stirred: could Sol Campbell, a scorer that night, crown his successful but controversial career with another major final? A big challenge will be how Arsenal's centre-backs handle the wanderings of Lionel Messi. With Zlatan Ibrahimovic a pivot up front, Messi breaks from wide to central positions and opens up shooting opportunities with that magical left foot. Arsenal will need to clamp down on his runs as he comes inside. Alex Song could be vital, but the Premier League club must be so wary of conceding free-kicks. Pep Guardiola's marvellous integration of his resources last season gave football purists a massive lift. Xavi and Andrés Iniesta, complemented by Yaya Touré, made up the perfect midfield threesome. They create goals. They rarely force goals. If Arsenal leave space while attacking, their gamble may backfire, though Thierry Henry is not as quick now as he once was to exploit clear ground on the counter. There are two wonderful games in prospect, but the main question will surround Arsenal's work defensively at the Emirates. They must not allow Barcelona to snatch an away goal if they are to stand any chance of making progress into the semi-finals.

Key clash
Cesc Fábregas v Yaya Touré

The tall, long-striding Touré looked, to my pundit's eye, the perfect replacement for Gilberto Silva or Mathieu Flamini in the Arsenal team. Song has surprised since – credit to Arsène Wenger for that much. Here, against the diminutive yet canny Fábregas, who commands the ball no matter how tightly marked, we will see a keen duel. Fábregas is never flummoxed, paces his passes beautifully, and will need to be at the top of his form against Touré who is a genuine marker and interceptor who does not rely upon fouling..

Bayern Munich v Manchester United

The thorough and supremely confident Louis van Gaal will relish this opportunity. Having stuttered badly at the beginning of this season and come under considerable criticism, Bayern Munich have steadily found their form. Up front Ivica Olic, a blur of energy, runs speedily down the channels while Franck Ribéry has regained his fitness and trickery on the flank. Anatoliy Tymoshchuk is vital to their central protection, while Mark van Bommel continues to contribute despite his lack of pace. Furthermore, Arjen Robben has had a new lease of life. But overall United have a younger and more athletic squad and are undoubted favourites. They are stronger in the vital central defensive area and, of course, Bayern do not have a jewel like Wayne Rooney.

Key clash
Franck Ribéry v Gary Neville

Ribéry has that rare gift of being to able to induce the full-back towards the challenge then, cleverly, lift the ball over the opponent's leg to wriggle free. He will not necessarily out-pace Neville. Rather, he will come inside on his right foot in search of space to exploit. Yet Neville's maturity and experience will ensure he copes far better than the younger Rafael.