By Kurt Bullard
The NFL is months away from starting, but even in the midst of March Madness, the league managed to grab headlines. Yesterday, the NFL announced that it would move the touchback to the 25-yard line, inciting a lot of backlash from the media and fans alike. At the surface, this looks like a move to protect kick returners by encouraging more touchbacks and therefore fewer full-speed collisions between players to most people, except perhaps Jerry Jones. The rule change is sure to have some impact, whether in this realm or in other unintended ones. I’ll run through to see how valid some of the worries that people currently harbor are about the rule change.
Claim 1: Returners Will Leave the End Zone Significantly Less
To examine this idea, we can look at the 2015 kick return logs and see how many times it would have been advantageous to return a kick. Last year, by parsing through data from NFL Savant, I found 2,778 kickoffs that were not onside kicks, kicked out of bounds, or called back due to penalty. Of those, I identified that 1,089 kicks were returned, whereas 1,689 kicks went to the end zone only to never be taken out. That means 39.2% of kicks were actually returned last year.
But this surface analysis fails to identify how many kicks should have been taken out. So, I looked at how many should have been returned, using whether or not the returner got to the 20 as a proxy for success. Of the returned kicks, 647 made it past the 20-yard line, meaning that 59.4% of the kicks that were returned were better than getting a touchback, whereas 40.6% should not have been returned (in retrospect).
Knowing that 40.6% of returned kickoffs should not have been returned, I can predict the rate at which kicks will be returned next year, assuming that returners exercise similar judgement. Last year, 380 kicks (13.7% of total kicks) made it past the 25-yard line upon return. I will make therefore make two assumptions: the same number (380) of returns make it past the 25-yard line this year, which would be the new better-than-touchback threshold, and these 380 returns represent 59.4% of the total returns on the year (the same percentage that were better than touchbacks last year). Under these assumptions, we can then estimate that the percentage of kickoffs returned is the percentage of kicks that should be returned (13.7%) multiplied by the inverse of the percentage of kicks that should have been returned (59.4%), which yields a prediction of 23.0% of kicks being returned. This is a rough estimate, but still somewhat alarming that only one out of five kicks might be returned next year.
So teams will still return kicks, but they might do so at a rate that is about 50% of last year’s rate.
Is This Fear Justified?: Somewhat
Claim 2: It Will Be In Some Team’s Interest to Never Return
I checked whether it would have been in some team’s interest to maximize expected points by never returning kicks in the coming season. I calculated the average expected points added for each team on kicks on which they attempted a return. It yields the following table:
In order for a team to be incentivized to never leave the end zone, the average expected points of a return has to be higher than the expected point value at the 25-yard line, which is 0.58 points. As is evident from the chart above, half of the team would have been better off never leaving the endzone. Ever. Of course, decision-making will change so that teams will be more judicial in taking the ball out, but it does signal a big change coming up.
Most likely, the bottom half of the league will adjust to the new rules and will exercise more discretion on kicks next year, raising the expected points added on average above the 0.58 threshold.
Is This Fear Justified?: After adjustments, probably not
Claim 3: It Will Be Too Easy To Score
Giving the offense an extra five yards on a touchback is an obvious boost to the offense, but it’s not clear how much of a boost it will be. To see, I calculated the return team’s actual expected points added on all kickoffs last year, both touchbacks and returns alike. The combined expected points added on all of the kickoffs last year was 1,202 expected points; of that, 628 came from actually attempting a return. I then calculated the optimal expected points that were possible if each returner made the optimal decision on whether to attempt a return or not, assuming that when a returner takes a touchback, it is the optimal decision. Under these assumptions, returners could have added 1,305 expected points if they always made the right decision, meaning they got 92.0% of the expected points from returning that they could have.
I then calculated the same values, but now changing the threshold from the 20-yard line to the 25-yard line. The total expected points that the returners could have added is 1,849 points, 237 of which could have been added from actively returning kicks, and 1,611 of which would have come from touchbacks. If we assume that 92.0% of expected points from returning are actually realized, then the expected point value from returning next year—assuming these parameters do not change—is 1,482, which is 280 points more than last year. This is like adding a team that scores 17.5 points per game to the NFL. So scoring is bound to increase from the rule change, and from the looks of it, will do so at a pretty high clip.
Is This Fear Justified: Somewhat
So, while the worst of fears will not be realized, there’s no doubting that NFL is continuing to trend towards fewer kick returns and more scoring.