Guest Post (Jared):
WARNING: This is a long one, so wait until you’ve got more than a couple minutes. Or, if you’re struggling to kill time at work, you’re welcome.
As everyone knows, this year the NFL altered its kickoff rules, with the goal of enhancing player safety (and looking past the obvious contradiction with a game that emphasizes hitting people). As it was explained, kickoffs are a type play uniquely suited to injuries, as you essentially take two full teams of players and have them run at each other with a huge head start to build up speed. Concussions galore (remember Jason Short?)
That general conversation got me thinking about kickoffs more generally. Simply put:
Does returning a kick make sense?
When you receive a kickoff, there are really on 4 potential outcomes, only one of which involves any decision making:
1 – It’s an onsides kick and the kicking team is trying to recover it…let’s ignore these
2 – The kick goes out of bounds, incurring a penalty, or through the back of the end zone for a touchback…let’s ignore these too
3 – The kick is fielded short of the team’s end zone, and must be returned (you could conceivably take a knee, but that obviously not be the optimal decision).
4 – The kick is fielded in the team’s end zone, and is either downed for a touchback or returned
For this discussion, we’ll focus on number 4, a returner taking the ball out of the end zone.
I felt like there were lots of instances over this past season where a returner would field the ball deep in their end zone and bring it out, only to be stopped short of the 20 yard line (the spot they’d reach with a touchback).
In light of that, I wanted to take a look at the risk-reward trade-off involved in returning kicks out of the end zone.
Sure, a kick return has a small chance of scoring a touchdown, or providing the team with dramatically improved field position (I know that’s hard for Eagles fans to imagine, but I swear it’s possible.)
However, returns also expose teams to a couple additional risks (besides not reaching the 20). The first is a turnover, and a hugely damaging one at that (immediately gives the ball to the other team, who likely just scored, in your territory.) The other, less quantifiable, risk is that the team will sustain an injury. These may occur when the kick returner takes the ball out of the end zone, but not on a touchback, and as such should be considered by whoever is making the decision to return the kick.
So…Do NFL return men suffer from an incentive problem that causes them to behave in a way that reduces the chances of their team winning?
As a theory, it made sense to me. I assume NFL kick returners can maximize their income by scoring more touchdowns (contract incentives can be based on this very metric), whereas no one gets incentivized to take more touchbacks, even if a touchback is a safer decision. So it wouldn’t surprise me to see kick returners taking the ball out more than they should, to try and create the big plays that get them noticed and get them paid.
However, nice theory or not, we needed to actually gather some evidence to see if it’s true (or if when I’m yelling at returners to take a knee, I should probably just keep my mouth shut)
I gathered play-by-play data from this past season (although somehow Week 1 got cut out, so it’s just Weeks 2 through 17). That started me off with over 2,000 kickoffs from across the league (excluding onsides and squib kicks).
I then filtered out any kicks that didn’t make it into the end zone (But since the NFL moved the kicking location from the 30 to the 35, there weren’t as many of those as in years past).
Now, of the remaining kicks, more than half of them were downed for touchbacks (or the kick went out the back of the end zone, which I couldn’t completely control for given the data).
That left me with over 900 instances where a kick returner had the chance to decide whether or not to bring the ball out of the end zone and decided to go for it.
So, all that was left was to figure out whether they made the right choice or not (with one key caveat I’ll describe later)
To do that, I used what football analysts have termed Expected Points (http://www.advancednflstats.com/2010/01/expected-points-ep-and-expected-points.html)
The included link explains the concept much more effectively than I can, but Expected Points is related to the idea that field position matters. Having the ball on your own 1-yard line is much worse than having it at the 50, right? Well, Expected Points attempts to quantify exactly how much more or less valuable a particular spot on the field is (with additional complexity for down and distance).
For example, having the ball in a first and ten situation at midfield is worth 2 expected points. If your team starts in that scenario, in general, you can expect an advantage of 2 points over your opponent. Having the ball in a first and ten on your opponents’ 10-yard line is worth an expected 4.7 point advantage, which makes intuitive sense. The closer you are to the goal line, the more expected points that situation is worth. All values taken from Brian Burke’s model, which he graciously has shared.
On kickoffs, it’s pretty straightforward, because every kickoff will result with one team getting the ball in a first and ten situation.
Now, the model I used for my Expected Points estimates the value of a first and ten at your own 20-yard line (the situation in a touchback), to be worth approximately 0.34 points. That may not seem like very much, but remember, 80 yards on a football field is a long way to go.
With that as our baseline, we can take all the kicks returned and measure the expected points of the results. We also need to be careful of turnovers, because a turnover not only costs you the expected points from your possession, it also provides the opponent with more expected points!
But before we go there, I did mention something about a caveat to this analysis.
Here’s the issue, there’s obviously a bit of bias inherent in this sample. Kick returners, assuming they are well-trained and skilled (basically, not Reno Mahe) should be able to recognize good opportunities to return kicks. We should hope that returners can understand good blocking vs. back blocking and know when to take a knee.
If that were the case (and if my theory about greedy return men is wrong), then we’d expect to see returned kicks having a higher expected points value. Otherwise either the returners are making sub-optimal decisions related to winning the game, or they can’t read their blocking well.
So what is it???
Returns brought out of the end zone are better, providing 0.46 expected points rather than a touchback of 0.34 (sample is over 900 kicks returned).
This implies that returners actually know what they’re doing, and that they recognize when to bring the kicks out vs. when to take a knee. The incentives are not as misaligned as I theorized.
I also looked a little deeper; to see whether kicks farther into the end zone (like 6-9 yards deep) were any different.
Nope, nothing particularly different about them, although the shorter the kick, the better the starting field position when it is returned. But at least based on the data, it seems like returners are actually making the right return decisions.
But wait, there’s just one other thing.
A lot of this perception comes from the games I’ve watched this year. And it just so happens that most of the games I watched featured the Eagles. So what happens when we look at just THEIR performance (ranked near the bottom of the league in average kick return yards)?
When the Eagles returned kicks this year, and specifically brought the ball out of the end zone, they created an average of 0.16 expected points, significantly worse than simply taking a touchback. Now, a good portion of this score is skewed by one specific play, namely, Brandon Boykin fumbling a kick return against Carolina in week 12. But even when you remove that turnover, the results are still worse than if they had simply taken a knee every time.
The problem becomes even easier to spot if we plot the results of Eagles ‘touchback-eligible’ returns against those of the entire league.
The chart below illustrates the average starting position following kicks into the end zone which were returned, grouped in five yard increments (for example the 45 bin is for all kicks returned between the 41 and the 45 yard line…the 100 bin represents touchdowns)
See how the Eagles have absolutely no ‘touchback-eligible’ returns beyond the 30-yard line (I excluded Boykin’s fumble, which to his credit, was almost in Carolina territory at the time)?
What the team managed to do this year was take a higher-risk, higher-reward scenario, returning potential touchbacks out of the end zone, and collect exactly zero rewards! They would’ve been better off taking a knee on average (note: this assumes your offense is better than your special teams, perhaps a dubious assertion).
It’s hard exactly to know where the blame lies in this situation. Does it rest with the now departed special teams coach Bobby Abril (who, if everyone remembers, was billed as a ‘guru’ level hire when he was brought in from Buffalo)?
Does it lie with Boykin, a rookie kick returner who may have had trouble reading his blocks?
Does it like with Howie Roseman and the administration for an overall lack of depth that kept the Eagles from having a solid set of special teams players?
Maybe a combination of all of the above? (Probably)
The major takeaways from the analysis point to a few things:
– NFL kick returners know what they’re doing, and appear to have a good sense of when to bring the ball out of the end zone, even after accounting for potential turnovers.
– However, the Eagles would’ve been better off taking a knee every time the kick fell in the end zone. The team was SIGNIFICANTLY worse than the rest of the league. This is an underrated weakness of the team and, if it’s addressed, could help the Eagles rebound quickly.
– If the NFL really wanted to limit kick returns, and I’m not sure it did, it probably should have move the touchback spot to beyond the 20-yard line. (To eliminate returns completely, which wasn’t the goal, the league would want to see the Expected Points value of a touchback equal or greater than that of a return in the first chart above.)