Arsenal's victory at Chelsea was certainly impressive, but what I took away from it was how bad Petr Cech has become seemingly overnight. He was beaten three times at his near post, all of which were stoppable. It is the latest in a disturbing trend for Chelsea this season: their Opponents' Finish Rate is 3rd-worst in the league at 41.18%, behind only Bolton and Blackburn.
It looks even worse when you take a harder look at the data. This early in the season, one might suppose that Chelsea's struggles in this department might be the result of a tough schedule. In other words, perhaps the teams Chelsea is playing are very good at taking their chances. However, their opponents have posted an average Finish Rate of 26.84% when not playing Chelsea, below the league average.
Perhaps this is a function of the team instead of Cech: Chelsea's bad defending leads to easy opportunities which their opponents duly dispatch. Chelsea may be liable give up more fast break opportunities because Ashley Cole and Jose Bosingwa push up so high and more fast break opportunities generally lead to a higher Finish Rate. Or they may be susceptible to free kicks and corners, which although they do not often result in SOG, typically go in at a higher rate when they are on target. I don't really have any data on that, but it's possible that it's not Cech but rather a function of the way Chelsea play. Arguing against that is that last year Chelsea posted a 23.74% Opponents' Finish Rate, second-best in the league. Other than Villas-Boas, the personnel is the same, but yet the results are completely different.
Cech is only 29, not old by football standards, and certainly not for a goaltender. I'm really unsure what has caused this dramatic turnaround, and this may prove to just be a rough patch. However, it's such a dramatic difference that I can't help but wonder if this may be the fatal flaw in Chelsea's title challenge.