I can't believe they've gotten away with using the converted Mascherano for this long. Pique is obviously a great defender but Puyol used to cover for his weaknesses; lack of concentration especially. Since Puyol retired they've essentially being getting by on a glued together, jury-rigged defense. Douglas, Bartra, Montoya, etc. haven't really developed into the players we'd hoped, Alves is 32, Mascherano is 31, Jordi Alba and Aleix Vidal are far better going forward than they are defending. Vermaelen's struggled with injury and he and Mathieu aren't the really of the best quality, in my opinion. Selling Pedro and losing Rafinha to injury has weakened the squad over this season also.
The form of Barça's best XI, which is still one of the best teams in the world, has carried them to where they are now. I think recent results has shown the effect of a long season that has encompassed La Liga, Copa del Rey, the Champions League, the Super Cup and the Club World Cup.