I've been writing a lot about offensive run-pass balance lately, recommending that most teams should pass more often. So far I've ignored half of the equation--Defensive strategies matter too.
Unlike offensive play choices which are discrete defined options (such as either run or pass), defenses have a continuum of options ranging from a prevent defense to a goal-line stand. Defenses don't have to commit to one or the other. Instead, they can bias their strategy anywhere from 100% pass to 100% run.
With play-by-play data, we know what option an offense chose. Unfortunately, without coach's film of every game and an intimate knowledge of a teams' defensive schemes and intentions, it's nearly impossible to know where on the continuum a defense stood on any given play.
Still, it may be useful to see how often a team was run against or passed against, and see how successful each play type was. The table below lists each defense's proportion of passes faced on first downs. Also listed is the average success of each type of play as measured by Expected Points Added (EPA). The difference in average success between passes-against and runs-against roughly measures the imbalance in play selection.
For example, Detroit has faced 43% passes on first downs. Passes against them have averaged 0.65 EPA and runs have averaged 0.00 EPA. Perhaps teams should be passing more often against the Lions. The Vikings show the opposite indication--passes against them are far less successful than runs. Maybe offenses should run more often against the Vikings on first down.
For defenses, negative EPA numbers indicate better performance. In the EPA Difference column, high positive numbers suggest that offenses should pass more against the listed defense, and high negative numbers suggest that offenses should run more. You can click on the table headers to sort.
|Team||% Pass||vs Pass EPA||vs Run EPA||Total EPA||EPA Diff|
Against the Lions, offenses have scored an average of about 0.65 more points by passing on first down than by running on first down. Against the Vikings however, the reverse is true. Offenses have scored 0.54 fewer points by passing rather than running. But their respective opponents have chosen to pass against both teams at nearly an equal rate, about 43%. Does that make any sense? Why aren't offenses exploiting the relative strengths and weakness of their opponents?
Note: I limited the data to plays when the score is within 10 points, and to the first and third quarters when time is not a factor. This way, the effects of 'trash time' and hurry-up offenses are excluded. In this analysis I also limited the data to plays between the 20-yard lines.