Don Revie was right - playing dirty football is the key to success. This paper by Christos Papahristodoulou shows that in last year's Champions League, there was a strong correlation between the number of fouls a team committed and the number of points won (0.877) or goals scored (0.762).
The correlation between fouls and yellow cards is only 0.688.
Indeed, the correlation between points won and fouls is greater than the correlation between points won and goals scored, corners or shots wide. Dirty football, it seems, works better than attacking football; Arsenal and Barcelona might have been outliers last year.
What's more, there's a statistically significant positive correlation between goals scored and both fouls committed and being caught offside.
Chelsea's performance on Wednesday could suggest that Jose Mourinho and Didier Drogba know all this.