I read an interesting piece, can't remember who by, about how Alba is the reason for their defensive frailty this year.
That's a good point.
It seems like Puyols nor Pique (nor Mascherano but he's really never struck me as much better at CB than what you saw today actually) are confident at all in their movements.
That they're having to adjust to the lack of any cover from a FB sweeping back in behind to help if they press may be a huge part of it.
For whatever reason, when Barca were truly awe inspiring, there were three facets that together completely demoralized the opponent:
1) the possession
2) pressuring like wild banshees to win the ball back
3) Puyol or Pique sweeping up anything that you could squeeze through the pressure.
Now, as tough as they still are in the first two, without that third, it's just not as demoralizing to have 25% possession when you still end up with a similar amount of decent chances as they're getting.