UEFA Champions League
With Argentine playmaker Riquelme pulling the strings in midfield, Villarreal gradually stepped up the pressure.
Arsenal were fielding a new-look back four with Sol Campbell returning to the centre of defence in place of the injured Philippe Senderos.
Arsenal manager Arsene Wenger was forced to reshuffle his defence once more when Mathieu Flamini left the pitch with a hamstring injury in the ninth minute.