In general, sack data for team defenses is not super consistent from year to year. Since 1990, the correlation coefficient between sack rate (for defenses) in Year N and sack rate in Year N+1 is 0.27. The best-fit formula (using a linear regression cover the years from ’90 to ’16) to predict sack rate for next year would be to use a constant of 4.8%, and then add 26% of the defense’s sack rate from the prior season.
That’s not too surprising of a result, but I was curious whether adding each team’s concentration index would help make sacks more predictive. As it turns out, the answer is a little complicated. I ran the same regression as above, but used each defense’s concentration index as a second variable. The change didn’t improve the correlation at all, and the p-value on the concentration index variable is 0.65, making it essentially meaningless. But it may be a little more complicated than that.
The team with the biggest decline since 1990 in sack rate, year over year, is the 2008 Chiefs. In ’07, Kansas City had a sack rate of 7%, the 8th-highest in the NFL. In 2008, it dropped to just 2%, the lowest in modern NFL history. And in 2007, Kansas City had the second most concentrated pass rush in the NFL, largely based on Jared Allen and his 15.5 sacks. In ’08, Allen was in Minnesota, and the Chiefs didn’t have a single player more than three sacks. This makes perfect sense: KC’s pass rush was very good in ’07 but centered around a superstar defender; without him the next year, the pass rush fell apart.
Sounds simple, right? Except that’s just one example. In 2000, the Titans had the 2nd best pass rush but just the 28th most concentrated: six Tennessee defenders had at least four sacks, and another six had at least two sacks, while Jevon Kearse and his 11.5 sacks made up just 21% of the team’s sacks. This sounds like a diverse pass rush that should be more sustainable from year to year, but in ’01, the team’s sack rate basically fell in half.
Analyzing sack data is very complicated: you have to factor in regression to the mean, Game Scripts, and also the randomness involved with something that only happens once every 15 or so passing plays. That said, the table below shows the 50 teams with the most concentrated pass rushes since 1982. In other words, these were the teams that were built around just one or a handful of elite pass rushers:
| Rk | Year | Team | Con Index | Sacks | Sack Rate | N+1 | Change |
|---|---|---|---|---|---|---|---|
| 1 | 1989 | Green Bay Packers | 35.2 | 34 | 6.7% | 5.3% | -1.30% |
| 2 | 2014 | Houston Texans | 32.8 | 38 | 5.8% | 7.5% | 1.70% |
| 3 | 2012 | San Francisco 49ers | 31 | 38 | 6.3% | 6.1% | -0.20% |
| 4 | 2016 | Oakland Raiders | 29.8 | 25 | 4.4% | 0.0% | |
| 5 | 2008 | Indianapolis Colts | 29.1 | 30 | 5.9% | 5.5% | -0.40% |
| 6 | 2008 | Atlanta Falcons | 29 | 33 | 5.8% | 5.0% | -0.90% |
| 7 | 1984 | New York Jets | 28.7 | 44 | 7.9% | 8.8% | 0.90% |
| 8 | 2001 | New York Giants | 28.5 | 46 | 8.1% | 6.4% | -1.70% |
| 9 | 1999 | Arizona Cardinals | 28.3 | 33 | 6.3% | 5.2% | -1.10% |
| 10 | 2010 | Indianapolis Colts | 28.2 | 29 | 5.3% | 5.6% | 0.20% |
| 11 | 2014 | Kansas City Chiefs | 27.9 | 46 | 7.8% | 7.2% | -0.60% |
| 12 | 1994 | Washington Redskins | 27.9 | 28 | 5.3% | 5.2% | -0.10% |
| 13 | 2008 | Houston Texans | 27.4 | 25 | 5.0% | 5.2% | 0.10% |
| 14 | 2012 | Kansas City Chiefs | 27.3 | 27 | 5.5% | 7.4% | 1.90% |
| 15 | 2012 | Houston Texans | 27.1 | 44 | 7.0% | 6.2% | -0.80% |
| 16 | 1996 | Arizona Cardinals | 27 | 28 | 5.1% | 6.5% | 1.40% |
| 17 | 1982 | Buffalo Bills | 26.4 | 12 | 4.5% | 6.3% | 1.80% |
| 18 | 2011 | Dallas Cowboys | 26.1 | 42 | 7.2% | 6.2% | -0.90% |
| 19 | 2007 | Houston Texans | 26 | 31 | 5.4% | 5.0% | -0.30% |
| 20 | 2013 | Indianapolis Colts | 25.9 | 42 | 7.3% | 7.0% | -0.20% |
| 21 | 1994 | Buffalo Bills | 25.8 | 25 | 4.5% | 7.8% | 3.30% |
| 22 | 1988 | Green Bay Packers | 25.7 | 30 | 6.0% | 6.7% | 0.70% |
| 23 | 2016 | Atlanta Falcons | 25.6 | 34 | 4.9% | 0.0% | |
| 24 | 2009 | Indianapolis Colts | 25.6 | 34 | 5.5% | 5.3% | -0.20% |
| 25 | 1993 | Kansas City Chiefs | 25.5 | 35 | 6.3% | 7.2% | 0.90% |
| 26 | 2011 | Minnesota Vikings | 25.2 | 49 | 8.5% | 6.7% | -1.80% |
| 27 | 2015 | Houston Texans | 24.9 | 45 | 7.5% | 5.6% | -1.90% |
| 28 | 1988 | Philadelphia Eagles | 24.7 | 42 | 6.8% | 10.5% | 3.70% |
| 29 | 2012 | Dallas Cowboys | 24.5 | 34 | 6.2% | 5.2% | -1.10% |
| 30 | 1991 | Phoenix Cardinals | 24.5 | 25 | 5.3% | 5.6% | 0.30% |
| 31 | 2005 | Oakland Raiders | 24.3 | 36 | 6.9% | 7.7% | 0.80% |
| 32 | 1990 | Los Angeles Rams | 24.2 | 30 | 5.6% | 3.8% | -1.90% |
| 33 | 2010 | Dallas Cowboys | 24.2 | 35 | 6.1% | 7.2% | 1.10% |
| 34 | 2007 | Kansas City Chiefs | 24.2 | 37 | 7.4% | 1.9% | -5.50% |
| 35 | 2006 | Indianapolis Colts | 24.1 | 24 | 5.7% | 5.3% | -0.40% |
| 36 | 1989 | New York Giants | 24.1 | 39 | 7.4% | 5.7% | -1.70% |
| 37 | 1990 | Buffalo Bills | 24 | 43 | 8.6% | 5.5% | -3.20% |
| 38 | 2009 | Denver Broncos | 23.8 | 39 | 7.1% | 4.4% | -2.70% |
| 39 | 1994 | Atlanta Falcons | 23.6 | 32 | 5.2% | 4.4% | -0.80% |
| 40 | 2008 | Miami Dolphins | 23.4 | 40 | 6.8% | 8.3% | 1.50% |
| 41 | 2003 | Denver Broncos | 23.4 | 35 | 6.8% | 7.3% | 0.50% |
| 42 | 2010 | Baltimore Ravens | 23.4 | 27 | 4.3% | 8.2% | 3.90% |
| 43 | 1996 | Kansas City Chiefs | 23.4 | 31 | 5.5% | 9.6% | 4.20% |
| 44 | 2007 | Green Bay Packers | 23.1 | 36 | 6.3% | 5.0% | -1.40% |
| 45 | 2003 | Tampa Bay Buccaneers | 23 | 35 | 7.0% | 9.4% | 2.30% |
| 46 | 2011 | Kansas City Chiefs | 23 | 29 | 6.0% | 5.5% | -0.50% |
| 47 | 1992 | Philadelphia Eagles | 23 | 54 | 9.6% | 7.2% | -2.40% |
| 48 | 2000 | Pittsburgh Steelers | 22.7 | 38 | 7.0% | 9.5% | 2.50% |
| 49 | 1986 | Buffalo Bills | 22.6 | 36 | 5.9% | 7.1% | 1.10% |
| 50 | 1993 | San Diego Chargers | 22.6 | 32 | 5.4% | 6.9% | 1.50% |
| Average of Top 50 | 25.8 | 34.9 | 6.4% | 6.4% | 0.00% |
On average, these teams had a 6.4% sack rate in Year N, and that didn’t change in Year N+1. Again, there are many other factors to consider, but that’s an interesting result compared to the next table. This shows the 50 least concentrated pass rushes since 1982.
| Rk | Year | Team | Con Index | Sacks | Sack Rate | N+1 | Change |
|---|---|---|---|---|---|---|---|
| 1057 | 1986 | Houston Oilers | 8 | 32 | 6.1% | 6.6% | 0.5% |
| 1056 | 2013 | Cleveland Browns | 8.2 | 40 | 6.2% | 5.0% | -1.2% |
| 1055 | 2014 | Tennessee Titans | 8.2 | 39 | 6.7% | 7.2% | 0.5% |
| 1054 | 1987 | San Diego Chargers | 8.3 | 45 | 9.3% | 6.2% | -3.1% |
| 1053 | 1997 | Pittsburgh Steelers | 8.3 | 48 | 8.0% | 7.8% | -0.1% |
| 1052 | 2007 | Cincinnati Bengals | 8.4 | 21 | 3.9% | 3.3% | -0.7% |
| 1051 | 2016 | Pittsburgh Steelers | 8.4 | 38 | 6.1% | 0.0% | |
| 1050 | 2007 | Baltimore Ravens | 8.4 | 31 | 6.1% | 6.0% | -0.1% |
| 1049 | 1987 | Chicago Bears | 8.4 | 69 | 12.1% | 7.3% | -4.8% |
| 1048 | 1987 | Cincinnati Bengals | 8.5 | 40 | 8.1% | 7.4% | -0.6% |
| 1047 | 1998 | Tennessee Oilers | 8.6 | 30 | 5.5% | 8.8% | 3.3% |
| 1046 | 1984 | San Francisco 49ers | 8.6 | 51 | 8.5% | 8.8% | 0.3% |
| 1045 | 2004 | New York Giants | 8.7 | 39 | 7.9% | 6.6% | -1.3% |
| 1044 | 1987 | Houston Oilers | 8.9 | 35 | 6.6% | 7.6% | 1.0% |
| 1043 | 1997 | Dallas Cowboys | 9 | 38 | 7.4% | 5.8% | -1.6% |
| 1042 | 1985 | Houston Oilers | 9 | 41 | 8.2% | 6.1% | -2.0% |
| 1041 | 1987 | San Francisco 49ers | 9 | 36 | 7.3% | 7.3% | 0.0% |
| 1040 | 1987 | Washington Redskins | 9 | 53 | 9.1% | 8.0% | -1.2% |
| 1039 | 2010 | New England Patriots | 9 | 36 | 5.6% | 6.1% | 0.5% |
| 1038 | 2004 | Washington Redskins | 9.1 | 40 | 7.2% | 6.1% | -1.1% |
| 1037 | 2009 | Cleveland Browns | 9.1 | 40 | 7.1% | 5.4% | -1.7% |
| 1036 | 2006 | Atlanta Falcons | 9.1 | 37 | 6.7% | 4.5% | -2.2% |
| 1035 | 2008 | Jacksonville Jaguars | 9.2 | 29 | 5.9% | 2.7% | -3.2% |
| 1034 | 2004 | Buffalo Bills | 9.2 | 45 | 8.5% | 7.0% | -1.5% |
| 1033 | 2015 | Jacksonville Jaguars | 9.3 | 36 | 5.6% | 5.7% | 0.0% |
| 1032 | 1987 | Detroit Lions | 9.3 | 42 | 8.4% | 8.4% | 0.0% |
| 1031 | 2003 | Arizona Cardinals | 9.3 | 21 | 4.1% | 7.0% | 2.9% |
| 1030 | 2001 | Buffalo Bills | 9.3 | 34 | 7.0% | 5.9% | -1.1% |
| 1029 | 2004 | Philadelphia Eagles | 9.3 | 45 | 7.9% | 5.5% | -2.4% |
| 1028 | 2013 | Oakland Raiders | 9.3 | 38 | 6.5% | 3.9% | -2.5% |
| 1027 | 1990 | New England Patriots | 9.3 | 33 | 8.1% | 4.2% | -3.9% |
| 1026 | 2009 | San Diego Chargers | 9.4 | 34 | 6.2% | 8.8% | 2.6% |
| 1025 | 1986 | Miami Dolphins | 9.5 | 33 | 6.4% | 4.1% | -2.3% |
| 1024 | 2000 | Cleveland Browns | 9.5 | 42 | 8.0% | 7.2% | -0.7% |
| 1023 | 1995 | Houston Oilers | 9.5 | 30 | 5.1% | 6.3% | 1.1% |
| 1022 | 1987 | Dallas Cowboys | 9.5 | 50 | 9.2% | 8.1% | -1.1% |
| 1021 | 2015 | Pittsburgh Steelers | 9.6 | 47 | 7.1% | 6.1% | -1.1% |
| 1020 | 2014 | San Diego Chargers | 9.6 | 26 | 4.7% | 5.9% | 1.2% |
| 1019 | 1999 | New England Patriots | 9.6 | 42 | 7.5% | 5.1% | -2.4% |
| 1018 | 2016 | Carolina Panthers | 9.7 | 47 | 7.1% | 0.0% | |
| 1017 | 2014 | Indianapolis Colts | 9.7 | 40 | 7.0% | 5.6% | -1.4% |
| 1016 | 1983 | Denver Broncos | 9.7 | 36 | 6.4% | 8.3% | 1.8% |
| 1015 | 2013 | San Diego Chargers | 9.7 | 34 | 6.0% | 4.7% | -1.3% |
| 1014 | 1998 | San Diego Chargers | 9.8 | 37 | 6.9% | 6.9% | 0.1% |
| 1013 | 1984 | Atlanta Falcons | 9.8 | 37 | 7.9% | 7.3% | -0.6% |
| 1012 | 1988 | New York Jets | 9.8 | 44 | 8.6% | 5.2% | -3.5% |
| 1011 | 1997 | Philadelphia Eagles | 9.8 | 41 | 8.1% | 8.6% | 0.5% |
| 1010 | 1987 | Green Bay Packers | 9.8 | 34 | 6.8% | 6.0% | -0.8% |
| 1009 | 1989 | Cincinnati Bengals | 9.8 | 33 | 6.4% | 4.4% | -2.0% |
| 1008 | 2004 | Oakland Raiders | 9.9 | 24 | 4.7% | 6.9% | 2.2% |
| Average of Bottom 50 | 9.2 | 38.1 | 7.1% | 6.2% | -0.9% |
The pass rushes were a little bit better in Year N at 7.1%, but dropped to 6.2% in Year N+1. Is that statistically significant? Probably not, and a regression on the data as a whole tells us no. We’d probably need to do a deeper dive to draw any definitive conclusions. But if nothing else, just seeing the bottom and top 50 teams in sack concentration makes for an interesting post. For example, the 1986 Oilers had the least concentrated pass rush ever: Houston had 32 sacks from 17 different players!