As Ajay says Barca play through the middle. Their width comes from the full backs and they're there to purely stretch the defensive line and open gaps between defenders for short passes between defenders and the defensive lines to exploit. Chelsea to their credit didn't allow this. They defended narrow and deep forcing Barca to cross from out wide into a packed area. Chelsea gambled that they had the strength and height to deal with it. They did. Count how many times Alves tried to cross it but he hardly ever got behind the Chelsea defense and turned them. The game also highlighted to me why Barca may have an interest in Bale. Alves on the right, Bale on the left as a attacking full back.
We and for that matter any English side are decades behind reaching the technical level the Barca are at plus as Chelsea proved if you are big, fit and organised it can be countered so you need a blend in the PL. A bit Bayern I guess. It seems that they have their own version of Carroll in Gomes. I wasn't hugely impressed with him either to be honest but to their credit they have power, pace and ability.
Personally though, if we could get somewhere near the playing style and ability of Bilbao we'd be doing very well indeed. I've been impressed with them and really enjoyed watching their Europa league games this season.