September 29, 2021

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Historical Aggressiveness Index, 1983-2020 |…

6 min read
Historical Aggressiveness Index, 1983-2020 |...

Earlier, this week we took a look at Aggressiveness Index numbers for 2020. Today, we’re going to look at historical Aggressiveness Index going all the way back to 1983.

Aggressiveness Index numbers center around 1.0 and generally describe how much more (or less) likely each coach is to go for it on fourth down compared to his peers; for example, a coach with 1.20 AI is roughly 20 percent more likely to go for it than an average coach historically would in equivalent situations. There are other methodologies now for measuring fourth-down aggressiveness, mostly based on win probability analysis: for example, the EdjSports head coach rankings or results spit out by Ben Baldwin’s fourth-down simulator. Each methodology will have small differences in how it ranks the coaches, but Aggressiveness Index differs from the others by measuring coaches not against what they should do but against the actual decisions made by coaches themselves.

The Aggressiveness Index excludes obvious catch-up situations: third quarter, trailing by 15 or more points; fourth quarter, trailing by nine or more points; and in the last five minutes of the game, trailing by any amount. It also excludes the last 10 seconds of the first half, and it adjusts for when a play doesn’t actually record as fourth-and-short because of one of those bogus delay of game penalties that moves the punter back five yards. Only regular season is included.

As we noted on Tuesday, those historical Aggressiveness Index baselines are a lot more conservative compared to how coaches are making decisions in today’s NFL. Philadelphia’s 2017 Super Bowl title helped push along a small-scale analytics revolution on fourth downs. Teams are not going for it as much as analytics would suggest, but since 2018 they are going for it a lot more than they used to. Last year, coaches went for it roughly 60% more often than we would expect based on historical baselines. 

We last took a look at historical Aggressiveness Index back in 2013. Since then, we’ve tweaked the formula to lower the strength of plays when the offense was on its own side of the field. These attempts were previously overweighted so that one random go in an unlikely situation would have a outsized effect on the overall AI. We’ve added 16 different years of play-by-play to our historical data, both 1983-1990 and 2013-2020. And we’ve added the last three years, where the league as a whole has been much more aggressive than in years past. This seems to be concentrated in two parts of the field: inside the 10 and between the 35-yard lines. Go-for-it rates between the opponent’s 10- and 35-yard lines are essentially unchanged.

A look at just the top dozen head coaches with a minimum of one year shows you how much things have moved in the last couple of seasons. The top five head coaches, and eight of the top 10, were coaching in the last two seasons. On the other hand, Vic Fangio of the Broncos (0.62 AI) is the only current head coach in the bottom 20, again with a minimum of one season.

The surprising names there are the older coaches, not the more recent ones:

  • Cam Cameron went for it on 8 of 11 qualifying fourth-and-1s for the 2007 Dolphins, as opposed to a historical coach average of 39%. He also went for it on both fourth-and-2 and fourth-and-3 in the second quarter against Oakland in Week 4. However, his numbers are a little juiced by that legendary game that the Steelers and Dolphins played in a Week 12 monsoon, where Miami went for it twice on fourth-and-long rather than attempting field goals over 40 yards.
  • Rich Brooks coached the 1995-1996 St. Louis Rams and loved his fakes. In Week 9 of 1995 againts the Eagles, the Rams ran a fake field goal to convert fourth-and-6 in the second quarter and then a fake punt to convert fourth-and-5 in the third quarter. Brooks also had the Rams go for it on 13 of 19 qualifying fourth-and-1s over the two seasons, although he never went for it on 15 qualifying fourth-and-2s.
  • I hope you will forgive me for not going through almost eight full years of Bruce Coslet teams, but Coslet might be the most surprising name on our list as the most aggressive coach of the previous century over a much longer period of time than these other top coaches. Coslet stood out for going for it instead of kicking long field goals from “no man’s land,” between the opposing 31 and 37. The historical average in these situations is to go for it 27% of the time. Coslet had his teams go for it on 32 of 53 qualifying opportunities, or 60%. Coslet also wasn’t afraid to be really aggressive on fourth-and-short. For example, in late 1996 after taking over the Bengals he had Jeff Blake throw a 12-yard pass on fourth-and-2 in a tied game against Baltimore Week 15, then had Blake throw a 16-yard pass the next week on fourth-and-1 when the Bengals were losing to the Oilers by less than a touchdown in the third quarter.

They don’t tend to keep coaches for very long but you can see the analytic angle of the Cleveland Browns with Kevin Stefanski, Freddie Kitchens, and Rob Chudzinski on the table above as well as Hue Jackson coming in high on the table below.

Before we get to a very, very big table with 131 different head coaches, here’s some other data about going for it in specific situations:

  • There are 11 different head coaches with a minimum of three seasons who have gone for it more than half the time on qualifying fourth-and-1 opportunities. The top six are all recent coaches, with Mike Vrabel, Doug Pederson, and Matt Nagy all over 60%. Don Coryell might be a surprise, at 54%. Then come three longer-tenured coaches including Bill Parcells (53%), Sean Payton (52%), and Sam Wyche (52%).
  • The head coaches with a minimum of three seasons who were least likely to go for it on fourth-and-1 include Butch Davis, Brian Billick, and Mike Nolan, all at 21%.
  • Doug Pederson has gone for it on 41% of qualifying fourth-and-2 opportunities, making him the only head coach with a minimum of three seasons who has gone for it on more than 30% of fourth-and-2s. Frank Reich is second at 29%, with Hue Jackson and Mike Vrabel at 24%.
  • The other specific situation we track is going for it between the opposing 31 and 37 instead of kicking a field goal or trying a coffin-corner punt. Three head coaches with a minimum of three seasons went for it at least 50% of the time in these situations. Matt Nagy leads at 74%, followed by Dave Campo (!) at 61% and then Coslet at 60%.

The best example of a longtime head coach getting more aggressive over the last three years is John Harbaugh. Harbaugh’s Aggressiveness Index through 2017 was 1.04. His AI over the last three years is 2.74, which would be the highest of all time for any head coach with at least one year. Another example, though not as striking, is Andy Reid. Reid’s AI through his long career until 2017 was 0.81. His AI over the last three years is 1.43.

Bill Belichick, on the other hand, has stayed the same as the league changes around him. His AI through 2017 was 1.33. His AI for the last three years is 1.38.