Guest column by Ben Baldwin

Proponents of committing to the run game argue that running the ball is the best way to sustain drives and keep a team's defense off the field. After drafting Rashaad Penny in the first round last month, Seahawks coach Pete Carroll explained that running the football "helps our defense." But is that really true? Given that 33 percent of dropbacks gain first downs compared to only 22 percent of rush attempts, we already have reason to be skeptical. Sustaining drives requires obtaining first downs, and the best way to get first downs is to throw the ball.

(Side note: as I explored on Football Outsiders earlier this year, there is no evidence that long drives carry any subsequent benefit for a team's defensive performance after accounting for field position. So even if rushing does help to sustain drives, it doesn't necessarily follow that defensive performance will improve.)

For this piece, I again examined public play-by-play data from nflscrapR from 2009 to 2017. I excluded the final three minutes of each half since time becomes a factor. Code is here.

First, let's take a look at whether longer drives tend to have more rush attempts. This is straightforward: they don't.

This figure includes the results of all drives of at least five plays, with a sample size of at least 20 drives. Regardless of how long drives last, the rate of rushes hovers between 41 and 42 percent. Already we can conclude that there is nothing magic about rushing in terms of generating long drives.

Below are series and drive results when teams rush or pass on first down, broken down by field position:

The advantage of passing on first down is roughly constant in terms of earning a first down, scoring points, and (for plays outside the opponent's 40-yard line) avoiding punting. Since about 44 percent of offensive snaps take place on first down, this is already a big chunk of game situations where passing is more beneficial than rushing.

For drives that start with very poor field position, drives that begin with a pass tend to last longer. This is likely partly because teams that are pinned very deep in their own territory prioritize avoiding turnovers more than scoring or moving the ball.

Brian Burke's earlier work shows that series that open with a passing play are more likely to earn a subsequent first down. Here is what Burke wrote in 2012:

"Coaches focus on making sure that their third-down plays are as successful as possible, which means using the first two downs to gain relatively assured bits of yardage using running plays to set up third-and-short, rather than third-and-long, situations. This mindset is intuitively seductive, but it's ultimately self-defeating [...] The best third-down situation isn't third-and-1 or even third-and-inches. It's converting on first or second down, before ever reaching third down."

For the remainder of this piece, I will look at plays that occur 20 to 90 yards from the opponent's end zone. Here is the average in this range for each of the outcomes under consideration on first-and-10:

While first downs almost always come with 10 yards to go, there is more variance on second downs. Here is how the rush/pass decision affects series and drive results based on yards to go on second down:

Regardless of distance, teams that pass are again more likely to score and less likely to punt. On second-and-4 and greater, passing is also associated with longer drives; for second-and-3 or less to go, passing and rushing are pretty similar. Teams that run on second-and-2 yards or less to go are more likely to earn a first down in that series.

Here are the results on third downs:

On third down, rushing becomes favorable over a wider range of yards to go. While rushing is better than passing in terms of earning a first down on the series with 3 yards or less to go, it is favorable in terms of avoiding punting with 8 yards or less to go, and in terms of plays per drive with 6 yards or less to go. This is likely because teams rush so infrequently in these situations (for example, only 10 percent of the time on third-and-4, and even less on further distances) that defenses do not expect it.

Let's be generous and say that plays on second-and-3 or less and third-and-6 or less (including fourth downs) are rushing downs. Only six percent of NFL plays since 2009 were rush attempts in these rushing down situations. For maximizing likelihood of scoring on a drive, the only situation in which rushing is about as good as passing is third-and-3 or less. Only three percent of offensive snaps since 2009 were rush attempts on third or fourth down with 3 or fewer yards to go (and as Football Outsiders has shown, handing the ball off isn't even the best play in some of these situations; QB sneaks are better when the distance is very short). Rushing downs are high-leverage plays, but they are so rare that investing in success in these situations is unlikely to be an efficient use of resources.

Furthermore, teams that are successful when rushing in short-yardage situations are not necessarily successful rushing in other situations. The correlation between a team's rank in rushing success rate (using the 45/60/100 measure) with 3 or fewer yards to go and its rushing success rate with more than 3 yards to go is 0.21. (The correlation is similar if we remove fourth-quarter plays, so this has nothing to do with playing from ahead or behind.) This is statistically significant, but not especially large. A possible explanation for this weak relationship is that the short-yardage samples are so small that success rate in these situations is mostly noise, but that is not a good argument for investment in the run game.

Conclusion

To review, here are our three main findings:

1) It is not the case that long drives disproportionately have greater rush/pass ratios.

2) Rush attempts that come in situations where running the ball is better than passing the ball in terms of extending drives are extremely rare.

3) There is not strong carryover between rushing success in short-yardage situations and rushing success in other situations.

Justifying an investment in the run game by saying it will help extend drives is misguided. If you want to get first downs, throw the ball (unless it's a short-yardage situation).

An economist by trade, Ben Baldwin uses large datasets to try to learn about human behavior. He covers the Seahawks for The Athletic. Reach him on Twitter at @guga31bb.