Recently I've been looking at run-pass balance on first downs based on a principle of game theory. When strategy mixes are optimized, the two strategies will ideally produce equal payoffs. If they aren't equal, then the better strategy should be selected until the opponent responds with his own counter-strategy. Results suggested that, in the NFL overall, the gains by passing on first down exceed those by running. In turn, this suggests that offenses should pass more often than they currently do.
However, every team has its own relative ability between passing and running. You can't just tell the 2009 Raiders to start passing more often. Their running game may actually be superior to their passing game in terms of expected payoffs, so while most teams should be passing more frequently, it's possible a minority of teams should be running more often.
I looked at each team's current run-pass balance in terms of average Expected Points Added (EPA) for each of their first down plays. Again, I limited the data to 'normal' football situations, 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 post I also limited the data to plays between the 20-yard lines. Inside the 10-yard line, running actually shows a higher payoff, so for now I want to isolate the pass-friendly part of the field.
Below is a table of each team and their percentage of first down passes through week 12 of the 2009 season. Each team's average EPA for runs and passes is also listed, followed by a total EPA for all first down plays. The final column lists the difference between the EPA for passes and the EPA for runs, which is an indication of imbalance in the respective payoffs of passing and running. Larger positive numbers suggest a team is better off passing more often, and negative numbers suggest running is actually the better choice.
|Team||% Pass||Pass EPA||Run EPA||Total EPA||EPA Diff|
About two thirds of teams have an imbalance that favors passing (positive difference), and one third of teams have an imbalance that favors running (negative difference). For example, Arizona tops the list of teams that should pass more. Their combination of a strong first down passing attack and anemic running game suggests they might want to increase their passing percentage well above their current 48%. At this point in their strategy mix, every run they call costs somewhere between a half and a full point on the scoreboard. Surprisingly, Detroit is second on the list, partially due to a woeful running game on first down.
At the other end of the spectrum is Tampa Bay. Their first down offense is below average both in the air and on the ground, but their passing game is especially woeful. Every dropback on first down is costing them over half a point. You might think this means they should run much more often, but they are frequently underdogs and may need passing's high variance outcomes plus some luck to win. But other teams with both a negative imbalance and a positive running EPA, such as Baltimore or Dallas, should consider running more often.
The sample sizes are relatively small here, ranging from 83 plays for the Raiders to 129 plays for the Steelers. I'd expect these numbers to regress significantly over the long run, and statistical significance is definitely an issue. However, we're not trying to declare a scientific truth here. Teams have to make a decision about their strategy mix based on the information available to them, and this is all we've got at the moment.
This is just a rough first sketch regarding what can be done with this concept, and there is more that we can do here. We can increase the sample sizes by including the early parts of the second and fourth quarters. We could also regress the numbers to an appropriate degree for a more realistic estimate. With better data, we can classify passes as deep, short or screen, and figure out what kinds of passes are helping and hurting--and do the same with run types.
Ultimately, play calling "balance" shouldn't be a league-wide commitment to run an arbitrary percentage of the time. Each team needs to balance its play calling by the weights of its own strengths and weaknesses.