Aggressiveness Index Update
by Aaron Schatz
If there's anything that statistical analysis in football has proved, it is that coaches are far too timid on fourth down. In fact, statistical analysis has proved this over and over and over again. It's been done. So is anybody listening?
The answer seems to be "maybe," but 2010 actually provided more evidence that the answer is "no." Two months ago, Steven Levitt of Freakonomics fame had a post on his blog titled "Are NFL Coaches Starting to Listen to Economists," with a few pieces of evidence that analysis on fourth downs and the pass-run ratio is starting to sink in with NFL head coaches. They mention that NFL teams are now passing more and running less than they did a few years ago, and also give an example of Mike Smith as a head coach who has been going for it frequently in fourth-and-short situations in opposing territory.
(By the way, this is a strange common tick for economists, to talk as if statistical analysis is only done by economists, but I digress.)
There's no doubt passing is up, but when it comes to head coaches listening to analysis on fourth downs, evidence is mixed. I went to look at fourth down "go for it" rates in what we'll call "qualifying situations." That includes all fourth downs in opposition territory, except for these situations:
- Third quarter, trailing by 15+ points
- Fourth quarter, trailing by 9+ points
- Last five minutes of the game, trailing by any amount
It turns out there were only three seasons between 1992 and 2010 where head coaches went for it on more than 16 percent of fourth downs, and two of those seasons happened to be 2007 and 2009. However, this past season, fourth-down attempts were down to their lowest rate since 2006. Overall, it looks like coaches are being more aggressive now than they were five or six years ago, but it is hard to say that they are definitely more aggressive than they were durnig the period 1994-1997.
Speaking of fourth downs, here are the Aggressive Index numbers for head coaches in 2010. Aggressiveness Index was a stat we introduced way back in Pro Football Prospectus 2006, created by Jim Armstrong. The computation for AI is a little more complicated than just giving the overall rate of "going for it" on fourth downs. Instead, the head coach's record in different "going for it" situations is compared to the league average, with the numbers weighted by the number of opportunities the coach had in each situation.
Leslie Frazier ends up with the highest AI for 2010, but that's based on a single play that actually exposed a hole in AI that we'll need to fix for the future. Frazier is given a lot of "aggressiveness" credit for going for it on fourth-and-14 in the second quarter of the Week 15 game against Chicago... but of course, he only went for it because it was the final play of the half, and an incomplete pass wouldn't actually give the ball back to Chicago. We'll fix this element of AI before we publish numbers in FOA 2011. The real most aggressive coach of 2010 was... once again, Bill Belichick, who is the most aggressive coach of the last two decades with a career AI of 1.84. (As an aside, the original Aggressiveness Index article in PFP 2006 very presciently mentioned that Belichick "distinguishes himself by going for it twice as often as average on fourth-and-2." Oh, if we had only known.)
Here are the most aggressive and least aggressive head coaches for the total period of 1992-2010. While we generally favor more aggressiveness, it's worth noting that not all aggressive coaches were great coaches, and not all great coaches were aggressive. The second-most aggressive head coach, between Belichick and Parcells, is Rich Kotite. Meanwhile, Andy Reid, Mike Holmgren, and Mike Tomlin are among the least aggressive coaches of the past two decades. So is Rex Ryan, although I have a sneaking feeling that's related to his offensive personnel rather than his own personal preferences. After all, I can't think of a head coach who is more aggressive than Ryan on the other side of the ball.
Bill Cowher was second on this list when we ran it in PFP 2006, but it turns out he was a little less aggressive in his first few seasons as Pittsburgh's head coach, so he drops down a bit on our new list. So much for my frequent comment about "the holy triumvirate of Bills." Nothing with Rich Kotite in it can possibly be a holy triumverate.
|Most and Least Aggressive Coaches, 1992-2010 (min. 100 attempts)|