Chelsea's Rough Patch (Part I)

Chelsea seem to have finally come out of the mid-season rough patch, where they slipped from top of the table to 5th place. However, the reasons for that decline are still unclear. Some have, for example, attributed it to the firing of Ray Wilkins. Recently, ESPN reported that Ancelotti attributed the decline to their pursuit of "sexy football".

(To be fair to Ancelotti, he does not say this exactly in the article. Nowhere does the word "sexy" appear in a direct quite. And Ancelotti merely says that they might have done better by parking the bus when they were in poor form rather than continuing to play their game the usual way. However, Chelsea's usual game is not sexy either.)

While the root cause of Chelsea's rough patch remains a mystery, the statistics are pretty clear about what went wrong on the field:

	Offense	Defense
Season (So Far)	1.692	0.501
Rough Patch	1.761	-0.024

The offensive number tells you how many goals Chelsea would score during an average match. This number stayed essentially unchanged during the rough patch. (A difference of .07 is just noise.) Chelsea have had the 3rd best offense so far this season (after Arsenal and Manchester United), and during the rough patch they had the 4th best. So not much changed offensively in either absolute or relative terms.

The defensive number tells you how many goals Chelsea would prevent the other team from scoring, that is, how much their defense reduces the average goals scored by their opponents. A drop of 0.5 (half a goal) is NOT just noise. In relative terms, Chelsea has the best defense over the season so far, but during their rough patch, they slipped to 13th in defense, worse than the stalwart defenses of Wigan, Blackpool, and Arsenal.

The lesson: Chelsea started losing matches because their defense fell apart.