Arsenal Football Formation

Lineup (3-4-2-1)

1 possibility for how Arsenal could match up against Barcelona

Barcelona's goals mainly come from their attacking trident Messi 40, Pedro 19, Villa 18 (next is Iniesta with 7)
None of those are big players, so ability to mark man and track runs more of a factor for Arsenal defence. Djourou could act almost as a sweeper, mopping up mistakes, interchanging with Song if necessary.

By playing Clichy on left of back 3, with Gibbs at Wing-back + Arshavin as outlet on that side it pins Alves back and protects from Barca cutting in from right wing via Pedro, Messi, or Iniesta.

On the right side Abidal not such a threat offensively, but would be worried about pushing too far forward with Walcott to take care of.

In the middle it's a simple 3 v 3, who wants it more?

And RVP provides the fulcrum to attacks, with Walcott and Arshavin rushing to support.