The Best Defensive Player in the NFL is...Neil Rackers?

My previous look at place kickers considered field goal kicking. Accounting for attempt distances and home field environment (dome, warm, etc.), I estimated that one standard deviation in FG kicking accuracy results in about 2.3 more successful FGs per season (worth 6.7 points). In this article, I'll look at kick offs and how they affect the ability of the opposing team to score.

Starting field position is obviously an important factor in scoring. The closer an offense is to scoring position, the fewer consecutive first downs are required to get there. A kicker who can kick deep can help his team by giving his defense more opportunities to force a punt or a turnover before his opponent is able to move into scoring position. Further, if the opposing offense is stopped, his offense will receive possession of the ball that much closer to scoring position on its own.

Kick off depth is easily measured, but the resulting field position is dependent on kick return and kick coverage performance. To isolate the performance of the kicker from the rest of the kick off squad, I ran a quick linear regression that estimates the expected resulting starting field position based on the depth of the kick. Average kick distances and return yards for each kicker (with >20 kick offs in a season) in the 2004-2006 seasons are plotted below. (Kicks that result in touchbacks are excluded at this point because there is no return. They will be factored back in later.)

We see that the deeper the kick, the longer the return. The longer a kick travels the more time and space the returner has to run before being met by the coverage team. Not every yard of extra kick distance translates into field position. About half of each marginal yard of kick distance is given back up in the return. If one kicker kicks 60 yd kicks, and another kicker kicks 70 yd kicks, the second kicker will only benefit by 5 yds of resulting field position after the average return.

Now we can calculate the expected resulting field position for each kicker in the NFL. Touchbacks are now factored back in. The expected starting field position of each kicker over the previous three seasons ranges from the 23.7 yd line to the 31.4 yd line. The average is the 27.4 yd line with a standard deviation of 1.49 yds.

Click on the table headers to sort.

KickerSeasonsKOsAvg DistTB PctExp Fld Pos
Neil Rackers320667.930.623.7
Michael Koenen214764.218.424.8
Paul Ernster17567.925.325.0
Olindo Mare318465.727.625.0
Josh Scobee322565.422.725.6
Kris Brown320164.414.925.8
Stephen Gostkowski18165.514.825.9
Todd Sauerbrun210060.011.326.2
Joe Nedney213260.28.626.3
Sebastian Janikowski319363.615.426.3
Jason Hanson320464.115.226.4
Micah Knorr16164.424.626.4
Jeff Wilkins323363.48.426.5
Wade Richey15363.113.226.5
Rob Bironas214163.214.926.5
Jay Feely324963.915.126.5
Mitch Berger28965.15.226.8
Phil Dawson319161.410.026.9
Aaron Elling27063.52.926.9
John Carney29561.64.727.0
Shaun Suisham12664.10.027.1
Billy Cundiff312263.16.227.1
Jose Cortez13863.910.527.3
Paul Edinger212859.10.027.4
Jason Baker12463.04.227.4
Adam Vinatieri324763.510.927.4
David Akers320464.312.027.5
Rian Lindell322159.74.627.5
Matt Bryant211962.57.627.6
Craig Hentrich17357.64.127.6
Josh Brown324663.18.927.6
John Kasay319462.15.428.1
Jeff Reed324461.66.528.2
Dave Rayner215463.38.328.2
Nate Kaeding327062.65.628.3
Lawrence Tynes326061.25.428.4
Robbie Gould214963.36.828.5
Matt Stover312861.36.728.6
Shayne Graham325761.56.728.6
Ryan Longwell321859.63.728.7
Toby Gowin17663.09.228.8
Todd Peterson16156.41.629.0
Mike Nugent213760.02.229.1
John Hall28160.72.729.3
Martin Gramatica24660.94.429.3
Jay Taylor12157.00.029.4
Steve Christie17157.72.829.7
Mike Vanderjagt27859.03.330.0
Nick Novak24458.82.131.4

The Importance of Field Position

I think the best way to examine the football-significance of kickoff field position is to look at two contrasting cases. Let's compare the league's best kicker, Neil Rackers, with one of its recent "worst," Mike Vanderjagt, who was cut by the Cowboys last year. Racker's average expected field position was the 23.7 yd line and Vanderjagt's was the 30.0 yd line, a difference of 6.3 yds.

How important are those 6 yards? The field is 100 yds long, so are they 6% important? It's difficult to quantify, but here is one way to think of field position: In almost all cases, to move into scoring position, either for a TD or FG, an offense needs a consecutive number of first downs. The closer an offense is to scoring position, the fewer first downs it needs. In other words, lets think of a typical drive as a sequence of 1st downs instead of a sequence of plays.

In baseball, the game rests on the outcomes of at bats, not necessarily every ball and strike. Think of a series of downs as the equivalent of an at bat, and individual plays as pitches. We're not as interested in each pitch as we are with the outcome of the at bat. The analogy continues because to score in baseball, several consecutive successes (hits or walks) are usually required. In football, several first downs are usually needed to score. (And in both sports there is always the slim possibility of a home run/long pass or breakaway run.)

In the NFL, a successful first down yields 15 yards on average. So those 6 yards of field position mean that in 6 out of 15 cases, an opposing offense needs one additional first down more than they otherwise would need to score. That additional first down gives a defense one more opportunity to force a kick or a turnover. That additional first down could turn what would be a TD drive into a FG drive, or turn a FG drive into a scoreless one.

In any given series of 4 downs in the NFL, an offense succeeds in gaining another first down (or touchdown) 65% of the time. So defenses are able to interrupt the consecutive series of first downs 35% of the time. So 6 yds of deeper field position per kickoff reduces the probability the the offense will score.

(6 / 15) * 0.35 = 0.14 --> 6 yds of field position adds a 0.14 probability of interrupting a scoring drive.

(It was pointed out to me that series in the red zone are often more difficult because of the compression of the field, so not every series has an equal probability of success. That's true, however the red zone series happen on a TD drive whether or not the drive started on the 20 or the 40 yd line. The "extra series" that is sometimes required by a deep kickoff does not cause an additional red zone series. It would be on the front end of a drive and not in the red zone.)

Over the previous five years, NFL teams scored an average of 23.4 FGs and 34.6 offensive TDs per season, resulting in 312 pts per season. A 14% reduction equates to 43.7 point difference between Neil Rackers and Mike Vanderjagt.

312 * 0.14 = 43.7 pts per season

I know my favorite team sure could use an extra 43.7 points this season. Depending on how they are distributed, that would usually mean an extra win or two. However, only 37% of drives begin immediately following a kickoff. That would mean that the difference isn't really 43.7 pts per season, but:

0.37 * 43.7 = 16.1 pts per season

But, in a way, all drives originate from a kickoff. All drives' starting field position subsequent to a kickoff are biased by the kickoff result. For example, a poor kick that results in a starting field position at the 40 yd line will result in all subsequent drives being closer to the kicking team's end zone than otherwise, until another kickoff. For that reason, I think the real answer is a lot closer to 43.7 points per season than 16.1 points per season.

Additionally, an extra series on a drive means there are more plays that could result in a turnover. About 10% of all series result in either a fumble or interception. That further strengthens the effect of field position and the importance of deep kickoffs.

We began the analysis by comparing Rackers and Vanderjagt, who were extreme examples--about 4 standard deviations apart. If we repeat the above analysis by looking just a single standard deviation in kickoff distance (1.49 yds), the effect is 10.9 pts per season per SD.

My previous look at FG kicking estimated that every additional SD in accuracy resulted in 6.7 more pts per season. When compared to 10.9 pts per kickoff SD, it appears that kickoff performance is the more important aspect of place kicking. Interestingly, when Vanderjagt was cut in 2006 by the Cowboys, the news articles didn't bother to mention his short kickoffs, only that he didn't like to do it.

An Alternate Analysis of Field Position

Previous studies have examined the point value of various field positions. Perhaps the best has been David Romer's study regarding 4th down situations. To evaluate when coaches should "go for it" on 4th down, he evaluated the point value of a 1st and 10 from each position on the field. The figure below is from his study.

Between the 15 yard lines, the value change is linear--0.04 points per yard. A 6 yard difference, therefore, equates to 0.24 pts per drive. With an average of 182.6 drives per season, that's a difference of 43.8 pts per season--almost exactly the same result yielded by the "one additional first down" analysis.

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6 Responses to “The Best Defensive Player in the NFL is...Neil Rackers?”

  1. Tarr says:

    I don't see Elam on the list. Did you omit him intentionally to avoid the mile high effect? This brings up the broader point that kickoff distance is almost certainly affected by weather. This is much more intuitively clear than it is for field goal accuracy. The kicker is basically kicking as hard as they can with little concern for accuracy, so physics of air resistance dictate how things work out.

    Good point on how most media sources ignore this aspect of kicker performance. One of Football Outsiders' basics is "the most underrated aspect of an NFL team's performance is the field position gained or lost on kickoffs and punts". I would certainly be more interested in average kickoff length than field goal percentage if I were signing a kicker.

    It would be nice if you could throw a "hang time" variable into that regression, but unfortunately that data isn't readily available.

  2. Brian Burke says:

    Elam hasn't done kickoff duty since 2002. But you're right about the effect of air density. It would slightly affect the rankings of the kickers, but not change the overall significance of the field position.

    FO was evidently on to something. But it's not clear they understood why or could quantify the importance of kicks and punts. This result appears to confirm and explain their theory.

    One thing that remains to be examined is the return and coverage team importance. I'd expect that they are predominantly random, and kick depth is the one component that is consistent.

    I agree and would sign the big leg. I'd also go for it on 4th down a lot more often and not worry about FGs so much. (More on that later.)

  3. Tarr says:

    Elam hasn't done kickoff duty since 2002. But you're right about the effect of air density.

    Right, of course. And there's Ernster at the top of the list. So it's safe to say that altitude matters.

    You're right that this doesn't change the main conclusion (long kickoffs are very important), although it does call into question whether the rankings you gave are reliable.

    FO was evidently on to something. But it's not clear they understood why or could quantify the importance of kicks and punts.

    I think it's pretty clear how FO would quantify that importance. They assign an expected point value to field position, much like the Romer study. I'm not sure their table is exactly the same, but I'm sure it's very similar. That's how they come up with their special teams rankings.

    You've certainly added to their explanation by, essentially, separating the kicker from the coverage teams.

    One thing that remains to be examined is the return and coverage team importance. I'd expect that they are predominantly random, and kick depth is the one component that is consistent.

    While the year-to-year correlation of coverage teams is not nearly as consistent as offense and defense, it does have some consistency. I would be surprised if this could be entirely explained by kickoff depth. Some teams devote more roster spots to gunners and/or use more of their best athletes on coverage teams, and it's reasonable to expect this would have some impact.

  4. Brian Burke says:

    FO's analysis of field position is buried in their turnover paper, but you're right they do seem to understand it. But their kick off article was all very qualitative. Maybe it's because it was intended for a more general audience.

    (I think they got their field position value chart straight out of Hidden Game of Football. I actually came across that very article just the other day. I haven't read the book myself, but it's on my list.)

    Just watching special teams, it seems very chaotic and random. Plus, there aren't as many iterations of punts or kicks as there are offensive and defensive snaps. So we'd expect less of a random component in the outcome of off and def than ST.

    I just read an column yesterday from the Dallas Morning News by Rick Gosselin about how there are so many more kick return TDs this year, somewhat because teams don't use starters on coverage teams like they used to.

    I agree that kickoff depth wouldn't explain all of the consistency, but I'd bet a good chunk of it. Some of it might have to do with the kick returners a team faces. The NFC North has to kick to Devin Hester a lot more often than most other teams.

  5. Tarr says:

    Yeah, there's certainly a ton of noise and variance to it. In addition to returners, I think you have to consider blocking. I remember Deion complaining during his year in Washington that the blocking wasn't as good as it was in Dallas. Personally I think Deion was mostly getting old fast, but there was probably some truth to the blocking being worse.

    It would be a tough task to tackle in a comprehensive study. You have to separate (and possibly discard) the effects of kicker, coverage teams, returners, blocking, and weather/altitude. And then there's edge effects - does the return team get some sort of credit on squibs or out of bounds kicks?

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