Pellegrini plays 4-4-2 and still some predict a 4-5-1. Brilliant thinking.
I suspect Pellegrini will play the ones that are clever. Demichelis for Lescott, Garcia next to Yaya (unless Fernandinho is fit), and Navas to start with Nasri on the nench. Can't predict he will play either Clichy or Kolarov, but with Sanchez as big a threat as Messi, he might want to go for the former due to his pace.
Their defence is -like ours- the weak link. We need to overpower them (they will fall over like autumnleaves) and play very direct in a high tempo. They will not be used to that in their own league. It's risky, but imo the chance to win it in the end. We are not a team to play to keep a clean sheet, yet a 0-0 would give us opportunities at their place with Aguero and Fernandinho back (unless he can play tomorrow).
I hope we don't give them the respect we gave Bayern at home. They are the clear favourites. Let's give them a big fight and present urselves the best way possible. If we scrape through in the end we will have deserved it completely. Even if we wouldn't deserve it I couldn't care less for that matter.