Let’s talk about sacks

A couple of very intrepid researchers at pro-football-reference.com went back and watched game film from NFL games back to 1960 in order to assign individual sack total for players who played prior to 1982, which is when the league officially started keeping track of individual sacks. The league has been keeping track of team sacks though, both on offense and on defense.

I thought it would be interesting to look at team sack total throughout the history of the league both on offense and on defense. I wanted to see the best and the worst for each year- sacks gotten and sacks allowed. I chose to restrict this to the regular season. I also decided to adjust on a per game basis to make the numbers for the years when there were fourteen regular season games make more sense (also to adjust for the strike-shortened 1982 season). This will also help going forward when there will be seventeen regular season games.

Defense

First lets look at the sacks per game by year

I was surprised by how flat this has been, but it does make sense. The sack rate was much higher in the 70s, but there were also fewer passes so the net result is the total number of sacks per game has been somewhere between 4.0 and 6.0 for every season since the merger. If you look at the trend line, there is a slight downward trend, but not much. Adjusting for the number of dropbacks you get the chart below

If this trend continues, in about twenty seasons the sack rate will fall to five percent. The high was over nine percent in 1976.

This is why it’s virtually impossible for a team to get 72 regular season sacks like the 1986 Bears did - even with an extra regular season game. To get 72 or more sacks in a seventeen game regular season a team would have to get 4.3 sacks per game. If you look at the sacks per game below for the league leading defenses, you can see that only a handful of defenses have ever been able to do that.

There have only been thirteen seasons where a defense has been able to record 60 or more sacks and no team has reached 60 since the 2013 Panthers did it. In total only 25 defenses have ever gotten more than 60 sacks and only a handful of teams have even gotten above 4.3 sacks per game. Those teams are listed below:

1. 1984 Bears - 4.50 per game
2. 1989 Vikings - 4.44 per game
3. 1987 Bears - 4.38 per game
4. 1976 49ers - 4.36 per game

That’s it. Only four teams have ever gotten enough sacks to break the record of 72 - even with an extra regular season game. FWIW, the average sacks per game from the league leading team throughout NFL history is 3.60. Meaning that we should expect the league leading team to have something like 61 sacks going forward with the seventeen game schedule.

The Broncos have only led the league in sacks three times: 1971, 2012 (tied with the Rams) and 2015. From a futility standpoint, the Broncos have twice had the fewest sacks on defense - 1979 and 2010. Only four defenses in league history have been so bad that they did not ever record one sack per game

1. 2008 Chiefs - 0.63
2. 2018 Raiders - 0.81
3. 1981 Colts - 0.81
4. 2009 Jaguars - 0.88

Two teams came dangerously close to making this list, the 1972 Patriots who had fifteen sacks in fourteen games and the 2020 Bengals who had seventeen sacks in sixteen games.

Offense

While there may have not been many defenses to record 60 or more regular season sacks, there have been plenty of offenses to allow 60 or more sacks. If we set this bar at seventy sacks, there have been only six teams to allow 70 or more sacks in a season, but we should note that the 67 allowed by the 1976 Lions ranks high on the per game basis. For a sixteen game regular season, 4.4 sacks allowed per game works out to 70 sacks.

There are only eight teams to have allowed more than 4.4 sacks per game during the regular season and they are called out below starting with the worst team, the 1986 Eagles, who allowed a staggering 104 sacks - 6.5 per game.

So it’s hard to get a bunch of sacks on defense, but it’s also “hard” to give up a bunch of sacks on offense. We haven’t had a team give up more than 4.4 per game since the 2014 Jaguars (Blake Bortles’ rookie season).

On the flipside, it’s difficult to give up less than one sack per game, but plenty of teams have done that. The bar here is 0.6 sacks per game allowed. Only four teams have done that and none since 1991.

1. 1988 Dolphins - 7 sacks allowed (0.44 per game)
2. 1991 Redacted - 9 sacks (0.56 per game)
3. 1975 Cardinals - 8 sacks (0.57 per game)
4. 1970 49ers - 8 sacks (0.57 per game)

What should be noted with the Cardinals in 1975 is that they were giving that few at a time when roughly nine percent of all dropbacks resulted in a sack. The same could be said of the 1988 Dolphins. 1988 was at the tail end of the golden era for defenses getting sacks (and for offenses giving them up). Astoundingly the Dolphins lead the lead in fewest sacks allowed for seven straight seasons, from 1984 to 1990. Similarly the Cardinals of the mid 70s were able to lead the league in protecting their QB for three straight seasons from 1974 to 1976. Oddly enough, both teams accomplished this during times when there was a spike in sacks per game, but the peak was higher during the mid 80s making the feat accomplished by Dan Marino and the Dolphins all the more impressive.

It should be noted that I did not adjust this for total dropbacks for comparative purposes between those mid 70s Cardinals and those mid 80s Dolphins. For completeness, the Cardinals had 355 passing attempts in 1975 while the Dolphins had 621 in 1988. This makes the Dolphins numbers all the more impressive since seven sacks allowed on 628 dropbacks (1.12 percent) is a sack rate that is crazy low even by 2020 standards.

From an individual quarterback perspective Peyton Manning and Dan Marino are tied for the lowest career sack rate at 3.12 percent.

Takeaways for the 2021 Broncos

The 2021 Broncos look, at least on paper, like they have an elite defense. It would appear that Vic Fangio now has a coverage group and pass rush to rival the ones he had during his best years as defensive coordinator with the Bears. I fully expect the Broncos to move into the top four in points in allowed in 2021, a place where our defense hasn’t been since 2016.

That being said, don’t be surprised if the Broncos do so by NOT getting a whole bunch of sacks. No defense has gotten more than four sacks per game this century (the 2000 season was last century - technically) and we had one team (the 2007 Ravens) who led the league in sacks with less than three per game.

One of the problems with looking ONLY at sacks is that it misses QB pressure rate by defenses. While sacks are great, getting pressure is much easier to do than getting a sack. Unfortunately, defensive pressure rate data before 2018 is behind a paywall where it is available.

In 2018, the best team in the league got pressure on 30.2 percent of dropbacks against them (the Rams), but they only recorded 41 sacks (eleven less then the two teams that led the league - the Chiefs and the Steelers (tied with 52). This was not the case in 2019 and 2020 when the Steelers led the league in both QB pressure rate AND sacks.

Our combination of an elite secondary and a healthy Bradley Chubb and Von Miller could dethrone the Steelers as the pressure champions in 2021, but the sack part may come down to how much we get from the defensive linemen. When the Broncos last led the league in sacks, 2015, we were able to get decent push from the three down lineman to collapse the pocket and keep the opposing QB from just stepping up to avoid Demarcus Ware, Shaquil Barrett and Von Miller. In 2015 that interior pressure was provided by Malik Jackson, Derek Wolfe, Antonio Smith and Sylvester Williams who combined for 41 QB hits and and 16.0 sacks. Miller, Ware, Barrett and Shane Ray combined for 67 QB hits and 28.0 sacks. As a team we had 52 sacks and no ILB or defensive back had more than 2.0 (T.J. Ward). The 2015 Broncos had 123 QB hits.

For comparison the Miller-less 2020 Bronco pass rush had 42 sacks and 93 QB hits. The outside linebackers (including Chubb here) has 46 of the hits and 21.5 of the sacks. The defensive lineman accounted for 34 of the hits and 16.5 of the sacks. So from a ratio standpoint the pressure was distributed in about the same way in 2015 that it was in 2020, it’s just that there was significantly MORE of it generated by the 2015 defense.