Although it is more of a back 2 or 1 at times the Barcelona back six is amazing:
Valdes, Alves, Puyol, Pique, Adriano, Mascherano
Valdes, Alves, Mascherano, Puyol, Adriano, Busquets
Mascherano really impressed me at CB this year.
Our back 6 does look good on paper although for most of this season I have not been impressed by Enrique and actually I think if we had kept Insua and let him develop he would be a better player and showed that at times this season. I just can't stand to watch Enrique do that little pirouette and stick out a leg. And is it me or does he seem to make a mistake every time we sing his song? Maybe I'm just being superstitious but I won't sing it any more.
Glen Johnson has definitely got better this season and I think a lot of that is to do with him being given the license to go forward, he looks a lot more confident on the ball and running at defenders ever since Kenny returned and looks like the player he was when Rafa signed him.
Agger, Skrtel and Lucas are an awesome combination which looked solid at the start of the season especially with Lucas playing as well as he did especially in those games against Man City and Chelsea.
But best in the world, potentially in the future, Enrique needs to get a bit more confidence when going forward and him and Johnson could make very useful wing backs if Lucas is there to cover defensively. However at the moment I would put Man City's above us in the Premier League and worldwide Barca's, Juve's and Real's. Juve's is probably the best defensively (only conceded 20 goals all season) but Barca and Reals are probably better going forward.
I would like to see us experiment with a 3 man defence with wing backs like Napoli or like we did when Kenny first came back, with Coates in there as well which would give the full backs more license to drive forward which would help Enrique especially.