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Adjusting team sack rates in the NFL for SOS

I’ve got sacks on the mind today. A few hours ago, I looked at the single-season sack records by various players in both the 3-4 and 4-3. Today I also want to look at things from the team perspective. In 2012, which team is the best at getting to the quarterback? You might think that’s as simple as looking at a list of defensive statistics and sorting by sacks, but I’d like to take a more nuanced approach.

There are two factors that heavily impact a team’s sack rate: the opponents they face and the number of passing plays they defend. Using sack rate instead of sacks helps to solve the latter issue, but we still need an opponent adjustment even if we use sack rate. It’s a bit tricky doing it correctly, because you need to iterate the results just like you do with the SRS. What I mean by that is the sack rate of the Denver defense will need to be adjusted for the sack rate of the Kansas City, Oakland, and San Diego offenses (among other teams), and those will need to be adjusted for the Denver defense (and all the other defenses those teams faced).

Once you properly iterate the results, what are the results? The table below shows the top defenses this year at getting to the quarterback, although note that these numbers exclude the games from week 15. The table shows how many pass attempts each team has faced, the number of actual sacks they have recorded and their actual sack rate; the next column shows the SOS adjustment to the sack rate, with a positive number indicating a difficult strength of schedule (i.e., they’ve faced teams that are difficult to sack). The last two columns show the SOS-adjusted sack rates and total sacks.

RkTeamATTACT SKSK RTSOSADJ SK RTADJ SK
1DEN506397.7%0.9%8.6%43.3
2CIN542437.9%0.5%8.4%45.7
3ARI426348%-0.5%7.4%31.7
4DAL429296.8%0.3%7.1%30.4
5CAR483306.2%0.9%7.1%34.2
6KAN389246.2%0.9%7.1%27.5
7STL489398%-1.2%6.8%33.1
8PHI467286%0.8%6.8%31.6
9HOU533376.9%-0.2%6.7%35.9
10MIA532377%-0.2%6.7%35.7
11GNB524356.7%-0.1%6.6%34.6
12BAL506305.9%0.6%6.6%33.3
13CLE531346.4%0.2%6.6%34.8
14NYG464316.7%-0.1%6.5%30.4
15SFO478326.7%-0.4%6.3%30.3
16PIT434266%0.3%6.3%27.4
17ATL463286%0.3%6.3%29.2
18BUF484316.4%-0.2%6.2%30.2
19CHI498336.6%-0.5%6.1%30.6
20SDG508254.9%1%5.9%30
21TEN481275.6%0.3%5.9%28.3
22SEA475326.7%-1.1%5.7%27
23NWE511285.5%-0.1%5.3%27.3
24NOR496255%0.2%5.3%26.1
25MIN515316%-0.8%5.2%27
26DET490306.1%-1.1%5%24.4
27WAS539234.3%0.7%4.9%26.6
28TAM541244.4%0.5%4.9%26.5
29NYJ446224.9%-0.1%4.8%21.5
30IND470245.1%-0.4%4.7%22.3
31OAK465173.7%0.7%4.3%20.1
32JAX464143%0%3%14

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