I don't think Arsenal have the player & manager to overcome Barca at Nou Camp..
Not that Barca unbeatable, but Arsenal do not have the players to harass, chase, at make cynical foul on Barca players to put off their rythm. However, Arsenal still a threat on counter attacking, since they got pacy player like Walcott.
Barca never strong at back, be it Puyol, Piquet or whoever play there, so the lost is minimal, but the worry for them is Ibrahimovic. I still can't figure why they exchange Etoo with Ibrahimovic. Old Etoo still much much better then Ibrahimovic.
Overall, Arsenal might be lucky to lose by at least two goals margin.