How NFL teams sequence plays is instrumental in their offensive success. Each play call in football is its own little game: the offense picks a play based on what it thinks the defense will do and what it thinks the defense will expect. The defense calls its play based on what it thinks the offense is most likely to do. A football game is not just one play, however, but a sequence of plays where the result of the previous play affects what the offense decides to call for the play at hand. Thus, I thought it would be a useful exercise to look at all of the two play sequences in the NFL since 2009 by down to see which sequences were most effective for the offense based both success rate and EPA per play (EPA stands for expected points added and is an estimate of the change of an offenses expected points for a given play from one play to the next). Success rate is defined as the percentage of plays with a positive EPA.
I filtered out all sequences that happened on different drives because intuitively the last play on one drive should not have much of an effect on the first play of the current drive. I also only considered run and pass plays (i.e. no special teams) and filtered out garbage time (where the win probability at any point exceeded 85% or was less than 15% for the offense). Now, let us look at the data. Note, the first play listed is the play at hand while the second play is the play that preceded it (pass-run means a pass play preceded by a run play). The first chart shows the number of two play sequences for each of the four downs:
Now, let's look at the success rates of each play sequence by down:
Based on analysis done in the past, we should not be surprised that throwing the ball on first and second down, no matter the previous play call, is the most lucrative play calling strategy. Based on the disparity in success rates, however, teams are still using sequences with running plays far too often relative to passing plays. On later downs, we see that sequences involving rushes tend to be more successful. Again, we have seen the analysis that running the ball is effective when a team gets close to gaining a first down, and considering third and fourth downs often have shorter to-go distances, running the ball on those later downs should be more effective. This is especially true on fourth down, where if a team is running or throwing the ball in a non-garbage time situation, that team is probably close to the sticks. One more note about fourth downs is to focus in on the success rates of all four two play sequences. The success rates across the board are large relative to other downs which indicates that teams should be very aggressive with their play calling on fourth down. The only sequence with a success rate of less than 50% on fourth down is pass-pass, and if a team is passing on fourth down following a pass on third down, then that team is probably not especially close to the first down marker. Still, on all rushes and passes in the NFL the last ten years, the league average success rate is about 44%, so no matter the play call on fourth down or the one preceding it, going for it yields a higher success rate than average.
Finally here is a similar plot to the one above, except this time with EPA per play instead of success rate:
data from 2009 season through week 1 of 2019 season
data via nflscrapr