Run / Pass Play Selection: First Down

With all this individual play data at my disposal, I've been looking at the trends of play selection, particularly run v. pass (i.e., I'm not looking into field goal / punt frequencies).  My end goal is to come up with a way to roughly estimate under which scenarios a team would pass / run, and the certainty of that estimate.  Once I have a model which works fairly well, it'll allow me to do a few things: (1) I can determine, mathematically, what is a run scenario vs. a pass scenario.  Then, I can look at how well teams perform in each of these scenarios.  For instance, my off-hand example is during a definite passing scenario (down by two scores with 2 minutes left, for example), if a team runs the ball they can probably get about, what, 5 yards or so?  Basically, I can build a basic game theory grid: avg. pass yards vs pass defense, avg. pass yards vs. run defense, etc.  And (2) if I know when, on average, teams pass, I can determine which teams / coaches like to buck the trend, and see if bucking the trend is successful or not.

I'm going to consider modeling run / pass ratios for each down separately.  Logically, I'm starting with the 1st down.  Provided below is average run ratios, broken down by starting field field position.

So you can see a second-order relationship between field position and this ratio.  Also, it looks like the relationship changes around 65 yards, with the slope being more gradual from 65 to 0 yards.  For my purposes, I'll model these two portions of the field separately (0-65, and 65-100).

Next, the relationship between time and run ratio.

 There's a pretty big break at the end of each half, can't tell if there's a big difference between the end of the half and end of the game, right around 10 minutes left.  For now, I'm going both halves the same, except for the last ten minutes (break those out separately).

And finally, here's the relationship between point spread and run ratio.

Pretty linear relationship, breaking down when the spread hits thirty points.  Teams really give up when down by 40 or more.  In fact, I'm just going to go ahead and throw out all these values.

So, in summary, here's what I'm looking at: when the field position is greater and less than 65 (second order relationship); first 20 and last 10 minutes of the half (linear for the first 20, second-order for the last 10); and point spread up/down to 30 (linear).  In the near future, I'll develop some linear regressions through all of these scenarios, so, stay tuned.  I doubt the regressions will say anything earth shattering, but, you know, I can mathematically say how often teams run the ball in the last two minutes.

Going for it: The Numbers Against Punting

There's this high school football coach somewhere who will always go for it on fourth down.  I can see his reasoning pretty clear in high school, every punt is this adventure of teenage-level talent, of bad kicks and bad coverage and botched long snaps and botched blocking.  He would just rather risk giving the other team the ball at the thirty, and like his chances of converting a fourth-and-whatever.  And in certain situations I can side with him.  I mean, how likely is it that an offense will convert a fourth and inches?  At the very least, I kind of like the wacky play where a team will fake going for it to just draw the other team offsides.  If they fail, take the delay of game penalty.  The scene is a quarterback yelling like mad while all the players pretend to be involved.  I don't know, it's something.  Anyway, in this post I'll go into all the statistics I can think of for when a team should punt or go for it.  If anyone's curious, the data I'm using are from all NFL games from 2002 on, throwing out meaningless plays (taking a knee, hail marys at the end of halves, etc).

Below I've plotted up the average net change in yards (the distance of the punt minus the return yardage) based on field position.  My frame of reference is yards to go for a touchdown; so if a team's on their own 20, then the yards-to-go would be 80.

 

On average a team will gain roughly 40 yards in field position if they punt.  Things start to break down around 55 yards as touchbacks begin to occur.

So, if a team doesn't go for it, and punts instead, what are the odds that the opposing team would make it back to that original ling of scrimmage anyway?  I've plotted out the odds that the opposing team makes it back to the original punting location, again, broken down by the kicking team yards-to-go.  This data is all based on average drive lengths from a given field position (in this case, the field position dictated by a punt).  I define "making it back" to the original line of scrimmage as the opposing (or receiving) team having a first down past the punting line of scrimmage, or scoring a touchdown.

 

For the most part, there's about a 35% chance that punting (instead of failing on a fourth-down conversion attempt) will make no difference in net yardage, and a 65% chance that punting is worth it.  Things start to tick up right around mid-field (pretty soon after we start seeing touchbacks appear).  So, generally, the benefit a team sees in punting (instead of just going for the 4th down attempt) starts decaying at mid-field.

Now all the data above is predicated on failure.  What are the odds that a team will actually convert on fourth down?  There's really not enough fourth down attempts to achieve a statistically significant result, so below I've plotted out the third down conversion rates for a number of different yards to go for a first down.  I looked at fourth down conversion rates, and when I exclude the red-zone area, there's not much of a difference from third down.  I went ahead with the third down numbers, as it's a bigger sample set.

 

So for anything a yard or shorter to go, there's nearly a 70% chance that the down is converted, and for anything shorter than 3 yards, that percentage drops to 50%.  If you kind of squint at the data, if a team only has a yard to go they should always go for it.  After that, it's a gray area; but if a team's on the opponent's side of the field, they should more or less never punt if there's only 1-3 yards to go.

Recent Developments

Obviously it's been awhile since I updated anything.  And with the coming labor disputes, lock-outs, all that, it's an open question when I'll be able to produce any weekly power rankings.  So, with all this time on my hands, I'm going back to the beginning.

I've stumbled across a source of play-by-play data, and worked out a way to bring in all that data and manipulate it.  Average drives, scoring percentages, totaling up runs longer than 10 yards, negative yardage plays, all of that.  In the coming weeks, I'll be able to churn out alot of different statistics, analyses, data models, etc.  So stay tuned.