Sorry to chelsea fans, but i don't see barca losing 3 games in a row. In my opinion barca will win 4-1(or 2), messi will probably score at least one goal, for chelsea lampard will be the scorer(for the second one, ivanovic).
I think barca will again produce one of their greatest ever performance, like they did against Man U, Real Madrid(5-0 win) and Santos.
I won't be surprised if chelsea opt for a stalemate, but i can't see them going through. They have a huge task on them, they need to overcome a barca side that will be doing everything they can to restore pride after loss to real madrid.
I think Barca will win the game. The margin of the win depends if they can get their shooting boots on (if they can, a thrashing is possible), they were extremely wasteful in that first leg. Chelsea are capable of scoring an away goal from a set-piece and going through (2-1 is the most likely scoreline in this scenario, I'd say), they seem full of confidence atm whilst Barca...not so much - they've been looking a bit cumbersome lately, the lack of depth in their squad has been showing.
We all know Chelsea are going to park the bus despite De Matteo's pre match conference. When Barcelona eventually breakdown their defence, Chelsea will be forced to come out and play and that is when the massacre will start. 4-1 barca.