Arsenal will be travelling to a fortress.

Villarreal have yet to lose at home in Europe but the Yellow Submarine know that it is useless to play a defensive game. They

But Manuel Pellegrini's side will be fresh. The wily coach made wholesale changes and rested 10 players for last weekend's La Liga match against Real Sociedad. Defender Cesar Arzo, who saw action at Highbury, was the only man in that makeshift side as Villarreal lost 2-0 to Sociedad.

As Villarreal languish in 10th place in Spain, it is clear where their priorities are.

That is why they need to rest key players like Juan Roman Riquelme, who had a mixed game in North London. While he threatened at set-pieces, he was muted during open play. Now, with home advantage, you can expect the Argentinian to bite back.

Pellegrini has no choice but to attack right from the start. Once the whistle blows, the crowd will be expecting them to grab an early equaliser. If Arsenal can weather the storm for the first 30 minutes, they would have taken a huge step towards the final as the home fans could turn on their team.

It will be a battle of wills.

ARSENAL'S HEADACHE

The Gunners have a tough nut to crack. They know that 1-0 is not enough. They needed a second goal in London to kill off the Spanish side.

This season, despite having injuries to key players, Arsene Wenger's makeshift defence had done him real proud, keeping nine consecutive clean sheets in 829 minutes of European football.

But the Professor's plans has a major setback as Philippe Senderos is ruled out through a knee injury.

Wenger has no choice but to recall Sol Campbell, who has just recovered from a broken nose and suffering from a loss of form.

Despite their lack of experience, Senderos, together with Kolo Toure, Emmanuel Eboue and Mathieu Flamini, have been rock solid in the Champions League thanks to their coaching from former Arsenal great Martin Keown.

With the Swiss centre-back ruled out, the continuity and stability is disrupted. In addition, Campbell's lack of confidence and match practice could actually do more harm than good.

THE BIG BATTLE - JUAN ROMAN RIQUELME v GILBERTO SILVA

One reason why Riquelme had a relatively quiet game in Highbury was the sterling work of Gilberto Silva.

Wenger positioned the Brazilian in a holding midfield role to shield his back four against the dangerous playmaker and the plan worked well.

In the first leg, Riquelme was shackled although he did threaten with set-pieces. But in open play, Gilberto did a good job in minimising the effectiveness of the Argentinian.

We can expect the Professor to utilise a similar tactic at the Madrigal. Gilberto will be the pivotal figure in sinking Villarreal.

If he can nullify Riquelme, half the battle would have been won.

MAN TO WATCH - JOSE MARI

Even if Riquelme is silenced, he is still a genius at set-piece situations.

And during the first-leg at Highbury, Arsenal gave away too many free-kicks just outside the box and were lucky to escape unpunished.

The reason why so many free-kicks were awarded was that the Gunners were not prepared for the diving antics of Jose Mari (below).

The striker would fall over at the slightest touch. Once he is in possession on the edge of the box, he would roll over and feign injury even when no contact is made with a defender.

So far, Villarreal's success story has been a fairytale. They have transformed from an unfashionable club into a power in Europe. But when their pretty football is not effective, be prepared to see their ugly side through Jose Mari.

THE VERDICT

This is the Gunners' biggest test in Europe so far. They are up against a real cunning opponent.

Wenger benched Thierry Henry, Freddie Ljungberg, Cesc Fabregas and Eboue from his starting line-up against Tottenham but still had to send some of them back into action when they were chasing the game.

In contrast, Villarreal had the luxury to rest 10 first-teamers for the weekend fixture against Sociedad.

The Yellow Submarine needs an early goal quick to settle their nerves and having fresh legs will be a big boost. Also, their cause will be helped by Arsenal's loss of Senderos and they will want to exploit the weak link in Campbell, who has clearly lost a yard of his pace.

But the Gunners can still count on their iron defence and Gilberto's screening from midfield. That said, they still have to be wary of Mari's diving and Riquelme's threat.

Not all is lost. Arsenal have a tremendous team spirit. And only through their unity will they qualify for the final in Paris.
 will be forced to attack as they are chasing a one-goal deficit from the first leg.