While the kick return is perhaps the most exciting play in football, it is also one of the most dangerous. You don't have to be Sir Isaac Newton to know that players hurling themselves at each other while running full-speed in opposite directions is an accident waiting to happen. The particularly heinous detail here is that special team players are often the very minimum salaried players that the NFL should work the hardest to protect.
As such, hoping to increase touchbacks and decrease injury, the NFL moved the kickoff location forward from the 30 to the 35 yard line in 2011. Indeed, as illustrated in the associated figure, this resulted in a dramatic decrease in the relative percentage of kicks returned. As the margin of error bars illustrate, the percentage of kicks returned has been steadily declining ever since 2011, with even the 2015 season appearing statistically significantly lower than that of 2014. Note that the data was derived from aggregate kickoff info obtained on www.footballdb.com.
However, there are questions as to if this improvement was enough. This figure was generated in an attempt to visualize all kick returns from the 2015 season, which is sorted by location that the kick was originally fielded. This data was extracted from downloaded play-by-play information complied by nflsavant.com, which has the added benefit of allowing us to extract when an injury occurred on particular kick return or touchback. Note that cases of falling on an onside kick and lateral situations were excluded due to the respective simplicity and complexity, but pose perhaps greater risk.
In fact, in the three years of play-by-play data available on nflsavant.com, there were still 53 injuries on 2974 kicks (1.75% injury rate) vs. 13 injuries on 3297 touchbacks (0.33% injury rate). These respective percentages imply that the risk of an injury is 5 times greater on a return than on a touchback. And as the above figure indicates, more than 50% of returns are coming out of the end-zone, so if we could give returners greater incentive to down the ball, we might expect the number of injuries to decrease by around 50%.
Maybe cutting 53 injuries by a factor of 2 doesn't sound like a great saving to the average fan, but let's remember how terrible each of these injuries can be. In a week 4 kick return last season, the Cowboy's Lance Dunbar tore his ACL/MCL/patellar tendons on a return to begin the second half. It is important that we remember that there is an individual behind each of these statistics that is suffering a life-altering and potentially career ending injury.
In an effort to further protect players, the NFL announced this off-season that they would be modifying the location of touchback to the 25 yard-line after a kickoff in the 2016 season. The hope is that this probationary rule provides an additional 5 yard incentive for returners to take a lower risk touchback. If we increase touchbacks, it will theoretically reduce injuries in special teams players.
In fact, if we stratify the returns from the past three years based on those started from the end-zone and those from outside, we see some very different distributions in play. Clearly returners have incentive to down a kickoff caught in the end zone. However, with the median of the "out of EZ" distribution lying at 25 yards exactly, it's NOT clear that kickers would have incentive to keep booming their kicks to the end zone and beyond.
Still, not all kicks in the above distributions are created equal. The difference between deep kicks and shallow ones should have a dramatic effect on the resulting starting field position. If we further stratify our data by position the kick was fielded, we can bin how the return fared relative to the new 25 yard touchback location. Again, the error bars are 95% margins of error that allow us to tell if, in spite of the variation due to randomness, the average starting field position after the return is at or beyond the 25 yard line more than 50% of the time.
This breakdown suggests that the average kicker may minimize his opponents starting field position by attempting to kick exclusively between the 0 and 5 yard line. Still, as with all observational data, we may be dealing with a bias of NFL kickers only attempting to pin it in the 0-5 range with less than average returners. If this is attempted with more skilled returners in the league, they may find this strategy is actually less than optimal. In the end, some Bayesian methods based on prior return yardage may help kickers decide in real time which returners will get a booming kick and which a mortar. However, at the onset, many returners are unknown NFL commodities, so the prior of league average may suffice. Thankfully the league is using the next year to evaluate the rule in a probationary period so they may be able to easily abandon the rule if it has the adverse affect than intended. Still, this may be after we have already put some special players at additional risk.
