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New York Times: Post-Week 15, 2013

by Chase Stuart on December 18, 2013

in NYT

This week at the New York Times, I look at the dominant Seattle pass defense.

As the passing revolution overtakes the N.F.L., football fans have become immune to the avalanche of falling records. Teams are averaging 239 passing yards per game and completing 61.3 percent of passes, metrics that would be single-season records. Peyton Manning is on a pace to break the single-season record for passing yards and passing touchdowns, and there was discussion last week that he was not even the most valuable player in the league. Josh Gordon set records for receiving yards in a two-, three- and four-game stretch this season, and the Cleveland Browns lost each of those games. You can forgive fans for not being impressed by gaudy passing numbers when Philadelphia Eagles quarterback Nick Foles starts the season with 19 touchdowns and no interceptions.

The league average Adjusted Net Yards per Attempt this season is 5.97, which would also be an N.F.L. record. (The previous high was 5.93, set last season.) The Seahawks have allowed just 3.40 ANY/A, easily the best in the league (San Francisco and Carolina are second and third at 4.62 and 4.73). But since the ANY/A league average has been rising for years, we cannot just compare Seattle to teams of yesteryear. We also need to measure how far from the league average each pass defense has performed.

The simplest way to measure deviation from the average is to measure the standard deviation among all pass defenses in the N.F.L. In 2013, the standard deviation of the ANY/A ratings of the 32 teams is 0.93. As a result, Seattle’s pass defense is 2.76 standard deviations above the 2013 mean of 5.97. If the Seahawks can maintain that level of dominance, it will rank as the fourth best season since 1970.

By this method, the top pass defense was fielded by Tampa Bay in 2002, the year the Buccaneers won the Super Bowl. In 2002, Tampa Bay allowed 2.34 Adjusted Net Yards per Attempt; that season, the league average was 5.35 and the standard deviation was again 0.93. As a result, the Tampa Bay pass defense was 3.22 standard deviations better than average. In the postseason, the Buccaneers allowed just three touchdowns while scoring four touchdowns on interception returns.

You can read the full article here. Below are the top 75 pass defenses from 1950 to 2012 using this formula:

Year
Team
ANY/A
LGAVG
STDEV
value
2002Tampa Bay Buccaneers2.345.350.933.22
1988Minnesota Vikings2.155.020.893.21
1970Minnesota Vikings0.724.161.182.91
1982Miami Dolphins1.224.761.332.66
1985Chicago Bears2.744.860.92.37
1974Pittsburgh Steelers1.593.910.982.36
2008Pittsburgh Steelers3.175.71.092.33
1977Atlanta Falcons1.093.551.062.32
1980Washington Redskins2.364.871.082.32
2005Chicago Bears3.375.340.862.28
1998Miami Dolphins3.575.310.762.28
1965San Diego Chargers2.443.920.662.26
1969Minnesota Vikings0.964.671.652.24
1973Pittsburgh Steelers0.583.891.482.23
1987San Francisco 49ers3.215.040.832.19
1965Green Bay Packers2.315.011.242.19
2003New England Patriots3.265.20.892.18
1963Chicago Bears0.814.871.872.18
1986Chicago Bears2.634.961.072.17
1952Los Angeles Rams1.313.120.862.1
2006Baltimore Ravens3.645.380.832.1
1997San Francisco 49ers3.525.160.782.1
1962Green Bay Packers1.395.011.742.08
2010Green Bay Packers4.095.730.792.08
2001Cleveland Browns3.35.190.912.08
1961San Diego Chargers0.913.851.432.06
1994Dallas Cowboys3.765.380.782.06
1956Chicago Cardinals0.653.881.572.05
1991Philadelphia Eagles2.995.181.072.05
2004Buffalo Bills3.665.630.962.04
2009New York Jets3.485.651.062.04
2007Indianapolis Colts3.985.520.762.03
1969Kansas City Chiefs1.764.231.232.02
1990Pittsburgh Steelers3.245.291.022.01
1950Cleveland Browns0.493.151.331.99
1991New Orleans Saints3.065.181.071.99
1971Baltimore Colts1.673.931.151.96
1996Green Bay Packers3.125.141.031.96
2009Buffalo Bills3.575.651.061.95
1995San Francisco 49ers3.915.410.771.95
1964Washington Redskins2.314.61.181.95
2012Chicago Bears4.35.930.841.94
1997Green Bay Packers3.655.160.781.93
1967Green Bay Packers1.284.321.61.9
2008Baltimore Ravens3.645.71.091.9
2000Miami Dolphins3.295.211.021.88
1999Tampa Bay Buccaneers3.495.180.91.88
1986San Francisco 49ers2.954.961.071.87
1960Buffalo Bills2.24.0611.86
1975Oakland Raiders1.214.041.521.86

{ 8 comments… read them below or add one }

James December 18, 2013 at 10:30 am

Interesting that the famed 2000 Ravens defense didn’t make the cut, but the 2000 Dolphins did!

Reply

Ty December 18, 2013 at 1:01 pm

The 2000 Ravens had an elite pass defense, but it was their run defense that vaunts them so high in terms of all-time defenses. You couldn’t run on that team (2.7 YPC, only gave up 5 TDs ). They did this in a division with Eddie George, Fred Taylor, Jerome Bettis, and Corey Dillion.

Reply

Tim Truemper December 19, 2013 at 12:56 pm

If one looks at the PFR data base, the 1964 Redskins (# 66 on the list) are an interesting case.

Reply

Chase Stuart December 19, 2013 at 12:57 pm

How so?

Reply

Tim Truemper December 20, 2013 at 1:39 pm

To Chase, they had a 6-8 record. They also had a plus 20 turnover margin in their favor. It seems that there running game differential (they were fair on offense running but not too good for defense may have been a factor). Did not examine special teams, penalities as other factors though. Just when I saw that team on the list, and knowing the Redskins were not soo good during that decade, I decided to look at the team page and cursorily see what they were like.

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Dan December 21, 2013 at 10:16 am

Isn’t another name for this “z-score”?

I thought that was a standard name for this type of analysis. Is there any reason you chose to label the column “value” instead of “z-score”?

(I get that you wouldn’t call it z-score for the NYT audience, I’m talking about the table you posted here.)

Reply

Chase Stuart December 24, 2013 at 12:07 pm

No good reason, I suppose. I guess we’re past the point of worrying about making this thing too stats heavy.

Reply

Tim Truemper December 24, 2013 at 11:50 am

Looks like Z score- it is a distribution based on SD’s from the mean- and the scores are not “normalized”- that is, the difference between different individual scores are not made equal interval units.

Reply

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