Sorry to burst your bubble guys. I know you're all psyched about Barça's 4-1 destruction at the hands of Chivas de Guadalajara (a team los blancos beat 3-0 earlier in the preseason)--but you shouldn't be. Here are the facts: preseason results are completely non-predictive, Barça were the victim of a couple of the most brilliant goals I've seen in a very long time, and they were playing mainly their B-squad without Messi or Puyol entirely.
I mean, sure--it's always a nice surprise to see a our nemeses lose handily, but really, this game means very very little. It certainly doesn't mean that they're now going to play badly in the Supercopa, or that even that they're not favored anymore: they're still the reigning European champions, the team that eliminated us from the Champions League last season.
So yeah, enjoy the moment, but don't think that this loss makes los blancos' task any easier--if anything, it's going to be harder: there's no doubt that Pep Guardiola will take this loss to heart and use it to motivate his players, and fix the problems that he will have seen on the defensive (and offensive) ends.
Sorry to be such a bummer. If you want more reasons to be less excited, read on.
Messi: Barcelona have been without their dynamic goalscorer throughout the preseason. The little Argentine's presence literally gives Barça's offense its' fangs: without him, they have much less punch because they need his goalscoring ability, his lightning-quick diagonal runs that fit so perfectly with Xavi and Iniesta's ability to make those little through balls. But guess what, madridistas? He'll be back (and ready) for the Supercopa on August 14th.
Puyol: It has become abundantly clear that Barcelona's defense really only functions well with Puyol pulling the strings next to Pique. His replacements, the youngster Fontas and Segi Gómez are either too slow (Fontas), or too inexperienced to run the complicated tiki-taka defense. Barça's defense relies heavily on its offense--possession is their defensive system, so to speak--and because of that, inexperienced central defenders have a tough time adapting. But never fear, their are rumors that Puyol will be back for the Supercopa (though this is much more up in the air than Messi).
New attacking options: No matter how you feel about the Alexis Sánchez transfer (whether it was a waste to spend that much money on a backup), it has definitely improved their squad. He provides an incredibly dynamic scoring threat off the bench, and will no doubt play an important role in Barcelona's quest to repeat as European Champions. Plus, it's very possible that Cesc Fábregas (yeah, him), will come in from Arsenal in the next few days with the intention of making his debut against Real Madrid. Now that's a scary thought.
Like I said earlier, I'm sorry to burst your bubble. Barcelona is still a really really good team, and should be favored against anyone, no matter what their preseason results suggest. (And no, this wasn't meant as a reverse-jinx piece--though it does a pretty good job of it!).