Ed Bouchette has a good article, with Steelers defenders talking about Michael Vick. Neil Payne has two interesting pieces (here and here) on how winning early games is correlated with the final record for the season.
Brian Burke has made an interesting attempt to break down EP (expected points) data to the level of individual teams. I’ve contributed to the discussion there. There is a lot to the notion that slope of the EP curve reflects the ease with which a team can score, and the more shallow the slope, the easier it is for a team to score.
Note that the defensive contribution to a EP curve will depend on how expected points are actually scored. In a Keith Goldner type Markov chain model (a “raw” EP model), a defense cannot affect its own EP curve. It can only affect an opponent’s curve. In a Romer/Burke type EP formulation, the defensive effect on a team’s EP curve and the opponent’s EP curve is complex. Scoring by the defense has an “equal and opposite” effect on team and opponent EP, the slope being affected by frequency of the scoring as a function of yard line. Various kinds of stops could also affect the slope as well. Since scoring opportunities increase for an offense the closer to the goal line the offense gets, an equal stop probability per yard line would end up yielding nonequal scoring chances, and thus slope changes.