When the Champions League draw took place, I took a look at Barca's group and immediately asked the question "is Rubin Kazan a club or a Hollywood agent who got thanked at last year's Oscars?" Not anymore. To say that Barca losing to a little-known Russian champion at the Camp Nou is a shock would be a significant understatement. The Blaugrana had not lost a match yet this season. They had dominated Inter on the road and then beat Dynamo Kiev rather comfortably. They remain unbeaten in La Liga and ground out a 0-0 draw at the Mestalla over the weekend. This defeat comes out of the blue.
Or does it? Major clubs often stumble following international breaks because their players often return physically and emotionally spent. This would be especially true for Leo Messi, who played two crunch matches for Argentina and has had to deal with the stress of being criticized at home for not replicating his Barca form for his country. While Cristiano Ronaldo comes across as an arrogant prick, his total self-confidence has a lot of value as a footballer in that he seems impervious to criticism. Messi comes across as a humble, sensitive guy, which makes him a much more endearing figure, but it also means that it's more likely that he would be affected by the disappointment that is his national team. Anyway, it sounds like Messi didn't play well yesterday and that was a factor in the defeat.
Another factor is that Barca have a hole at left forward. Thierry Henry has alternated injuries with ineffective play so far this season. His replacement - Pedro - has some promise, but is young and inconsistent. The hole at left forward is exactly why Barca seem to be so gung ho on bringing Robinho to Catalunya in the winter transfer window.
A third factor is that Rafa Marquez is a suspect defender. It sounds like he was culpable for both goals. Marquez is not a first choice centerback. Pique and Puyol are the starting pairing and Dmytro Chygrynskiy was purchased to be the first replacement. Thus, I wouldn't be overly concerned, as we aren't learning anything new: Marquez is capable with the ball, but he is prone to make defensive errors.
Maybe there isn't that much to read into the loss. Barca dominated possession, hit the post on multiple occasions, and lost out in large part because of a wonderstrike. Barca opened last season with a loss to newly-promoted Numancia and they lost at home to last place Espanyol, so there is precedent for this excellent side losing to an inferior opponent. Also, it's probably unfair to put Rubin Kazan in the "inferior" category. They won the Russian league, which has been improving considerably over the past several years because of the infusion of oil money. (See: Zenit.) This loss isn't the end of the world. However, it does mean that Barca are going to have to get results in winter games in Russia and Ukraine, which is never easy. Their margin for error is now almost gone.