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!