By Andrew Mooney
A year and a half into the NFL’s amended kickoff rules, it’s safe to say they’ve achieved their intended purpose. In 2010, 16.4 percent of kickoffs resulted in touchbacks; a year later, that number rose to 43.5 percent. The teeth were taken out of what was thought to be one of the most dangerous plays in the game by simply reducing the number of times it occurred.
The kickoff rule change—specifically, kicking off from the 35-yard line—interests me not as a safety regulation, but as a method to examine teams’ decision-making. Have NFL coaches properly accounted for it in the way they instruct their special teams units?
My gut reaction says no. On a number of occasions this season, I’ve watched returners take the ball out of the end zone from eight or nine yards deep in the end zone, only to be stuffed at the 15, needlessly hampering their offenses with poor field position. It seems like teams should be settling for even more touchbacks than they currently are.
Of course, gut reactions are worthless for evaluations of this sort, so it’s time to go to the numbers. Using play-by-play data for the first four weeks of the 2012 season, I picked out every instance in which a team kicked the ball deep (i.e. not a squib or onside kick) and noted the receiving team’s resulting field position following the return.
It turns out that NFL special teams units are not being so irrational after all. On all long kickoffs (defined as any kick fielded by a returner inside his own ten-yard line), the average starting field position of the receiving team is at their own 23.5-yard line. Admittedly, this doesn’t offer a comprehensive picture of the question, since I’m most interested in just kicks fielded deep in the end zone, so I broke the data down further. Even on kicks fielded five yards deep in the end zone or further back, the average kick return yields better starting field position (a team’s own 22.5-yard line) than simply taking the touchback and heading to the 20.
However, bringing a kick out of the end zone includes an additional risk: fumbles. In the first four weeks of the NFL season, there were five fumbles on kickoffs, three of which were lost (a rate of about 0.01) at an average field position of the fumbling team’s own 20-yard line. Using Advanced NFL Stats’ Expected Points calculator, I found that a first and ten on one’s own 20-yard line is worth +0.34 EP, a first and ten on one’s own 23.5-yard line is worth +0.51 EP, and an opposing team’s first and ten at one’s own 20-yard line is worth -4.08 EP. The question now becomes if the one percent risk of losing a fumble is worth the extra +0.17 EP of taking a kick out of the end zone. It turns out that it is: 0.01*4.42 EP = 0.0442 EP, which is about four times less than the benefit of the extra yards gained from taking the ball out of the end zone.
But the decision to encourage kick returners’ apparent greediness may be good or bad depending on changes in the game situation. The variance in field position for kicks returned from five yards deep in the end zone or deeper is much higher than for kicks returned from further up, meaning that the set of outcomes is much more spread out. In other words, with a kick fielded deep, a team is relatively more likely to have a starting field position that is quite a bit different from the average. That means that if a team is behind late in the game, it’s probably worth while to take the risk of bringing a kick out of the end zone for the possibility of a big return and great field position. But if a team is protecting a late lead, it may want to simply take the touchback, instead of running the risk of starting its drive at its own 10-yard line and sacrificing ten yards of precious field position.
I have yet to examine the data for previous seasons to determine what the existing trend is here, but the verdict seems to be that, even with the new kickoff rules, a returner is usually better off bringing the ball out than settling for a kneeldown in the end zone—that is, unless he happens to be fielding a kick from Neil Rackers.
This post can also be seen on Boston.com here.