There has been some buzz recently for the new football league that is set to start next spring, the AAF (Alliance of American Football). Jeremy Fowler from ESPN wrote a nice article this week, which among other things covered the will of the league to not include kickoffs! One of the backlash that a similar proposal had received in the past in the NFL was what will happen to onside kicks – this was part of the game (even though it was only slightly better than a lottery ticket – to exaggerate a bit…). The AAF is planning to solve this by allowing the scoring team to get a 4th down play from their own territory if they want the ball back. Convert and you keep the drive, fail and the opponent gets the ball on that spot. What the article did not mention (and I believe the league has not yet decided on) is what the distance should be and where this drive should start. So I found this idea fascinating and I decided to give some suggestions and my opinion on this rule — is this the first ever analytics article for AAF?!? 🙂
As aforementioned a major concern is what will happen to onside kicks. The solution that seems to be emerging is to give the scoring team a fourth down in their own territory. However, what the field position and yardage to cover for a first down should be? Depends on the objective. Do you want to give the scoring team the same chances of recovering (and maybe scoring after the recover) as in the NFL’s onside kick? If yes, you need to set the distance to a value that will lead to conversion rate of about 18.5% – which is the onside kick recover rate. Following I present the conversion rate for 4th (and 3rd) downs in the NFL (granted AAF might be a level or a half level below NFL in terms of talent but these are fairly good numbers as a starting point), where the onside kick recover rate is represented with a horizontal red line.
It seems that 4th and 10 will give an advantage to the offense compared to the current NFL onside kick recover rate. So maybe a 4th and 15 will be more fair (again it depends on what the league is after in terms of allowing teams to get the ball back).
Another variable is where do you position the chains for this 4th down attempt. The idea would be to position them at the team’s own 35 yard line. However, what is also important is where the ball was typically recovered from an onside kick. That was the teams own 47 yard line, so if we assume a 4th and 15, this gets us to the team’s own 32 yard line, which is not that far from the 35 yard line.
Of course, here is where it can really get interesting. The league could allow the team to exchange part of the yardage-to-go for field position (and vice versa). Depending on the talent of the team’s offense or the opponent’s defense this can be a strategic decision. The league’s exchange converter will be a league-average, so individual teams might be able to exploit this. These exchange converters can be calculated from NFL data (and possibly adjusted for the AAF).
Kickoff returns and mortar kicks
The other part that needs to be considered is what happens after a score if the team does not want to attempt an onside kick. Where does the opponent get the ball? The simplest thing (and what I am assuming will end up happening) would be to get it at their own 25 yard line, similar to a touchback. However, this eliminates the ability of a good kicker to pin the offense close to their own yard line (or even a good return team get better field position). So here is another suggestion: have the scoring team choose the extra point kick distance and exchange it with field position for the ensuing drive (similar the starting position for a two-point attempt). For example, if I want to pin my opponent closer than 25 yards to their own territory I might take me kick PAT 10 yards out. Again we will need an exchange converter but again this can be done with appropriate data. For example, using some of the data from my paper presented in the Workshop on Machine Learning and Data Mining for Sports Analytics back in 2015 following is the success rate of a field goal as a function of distance:
The vertical line represents the current NFL kick PAT and we are interested in values greater than this. For the range of distances between 32 and 55, the drop seems to be a bit linear and in particular a linear model explains 85% of the FGs conversion rate. In particular, each 1-yard increase (beyond 32-yards) drops the expected points per FG by 0.014 points. Furthermore, the following is the probability of TD, FG and failed drive given the starting field position as taken from the original paper (so the touchback line is still the 20-yard line 🙂 ):
If we do the calculations each yard behind the touchback line (we used the 25-yard line) reduces the expected points from this drive by 0.027 (the linear model explains 94% of the variance). So it almost seems that there could be a simple 1-to-2 exchange rule between PAT and field position at the league average level. Every 2 yards behind the current PAT kick, will bring the offense back by 1 yard. Now it is clear that if you want to pin the offense all the way down to their own 1 yard line, this would mean increasing the distance of your PAT by about 50 yards, which will give you practically a 0% chance of making the extra point (falls out of the linear range we used above). This is still a decision the team could make based on their kicker and how he compares to a league-average kicker (and considering the opponent’s offense, time left, score differential, its own defense etc.). The team could even have the opportunity to choose closer distance for the extra point and give the opponent better field position (but I would not expect that to be the case). A similar idea can be used for (no) “kickoffs” after a field goal score. I.e., you can exchange distance for starting field position. Obviously a different exchange converter is needed. All of these could be similar to penalties – i.e., can be accepted or denied by the other team.
The only thing that has not been covered here is what happens with the return unit. In the above only the scoring team (kicking team) makes decisions and can decide where they want to pin the opponent’s offense. How can the (no) returning team simulate a return? A possibility would be again to enhance the above mechanism with an exchange between field position and yards-to-go for the first first down of the next drive. This could actually mean that the scoring team might choose to give the opponent’s offense a better field position for longer yardage-to-go (?) or to spice things up in a FG attempt the defense might also be allowed to offer the offense closer distance for the FG in exchange to yardage for better starting field position (offense can obviously accept/decline). Again data can come to the rescue for this. But well, I am not going to spill all the beans here, but if AAF is interested I am available for hire 🙂 But jokes aside, it is very interesting to see where this no kickoff rule will go and what will be the impact on collisions and player safety.