Slyboogy Mephistopheles - looking at the race lap analysis on the FIA site is really quite interesting from this race:
http://www.fia.com/championship/fia...013/2013-spanish-grand-prix-event-information
Perez was burning through his tyres much faster than Button - so much so that towards the end of each of his stints, he was often over a second a lap slower than Button (who continued to lap for several laps later!)
So why was Perez so close at the end? Well, that all came down to Button's appalling qualifying - but again, where can this be attributed to? Well, looking at the sector times, again it was completely down to the mistake he made in the final sector...
What can we conclude from this? Well, I think it is hard to argue that Button wasn't at least as fast as Perez during the race this weekend, and had they started from closer on the grid, then Perez would likely not have been in a position to challenge at the end (But obviously they did start quite a way apart)...
I think this race has raised an issue that I think has dogged Button through his career; when he's chasing a time, and trying desperately to make it through to (say) Q3, something tends to go wrong for Button, and he doesn't 'just' miss the cut, but often is a long way away from the cut - this race in 14th! This does seem to be a pattern for Button - rarely does he qualify 11th if he fails to make the cut - suggesting to me, at least, that when he's up against the wall, he may be "trying too hard..."