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Are Teams Afraid To Pass Against Seattle?

The Legion of Boom May Be Harmful To Your Offense's Health

The Legion of Boom May Be Harmful To Your Offense's Health.

We know that the Seahawks pass defense is historically good, but the title of this post sounds like it was written by a Seahawks homer, right? I mean, who else besides a green-and-blue fanboy (or maybe Richard Sherman or Earl Thomas) would write something as absurd as “Seattle’s pass defense is so good that teams are afraid to throw on them!!!”

The thing is, it’s kind of true. Seattle faced only 568 pass attempts (including sacks) during the regular season, the sixth fewest in the NFL.  Some of that is due to the Seahawks pace on offense and dominance of a defense that prevented sustained drives; even still, opponents passed on “only” 57.4% of all plays against Seattle.

Seattle ranked below average — 18th — in percentage of pass plays faced, but there’s a reason I put only in quotes. Seattle held an average lead over every second of game play this year of 5.6 points, the third best mark in the NFL. Denver and San Francisco were the only teams to play with larger leads, and they ranked 6th and 7th in percentage of plays faced that were passes. This is hardly a newsflash — teams generally throw often when trailing — but that wasn’t the case with 2013 Seahawks.

When Steve Buzzard used the Game Scripts data to determine defensive pass identities, he found that teams were more hesitant to pass against Seattle (once adjusting for the score and strength of schedule) than against any team in the league. I thought it would be interesting to take another crack at measuring this effect. We can use the score differential after each of the four quarters of the game to determine how many pass attempts (as a percentage of total plays) a team *should* face.

I ran a regression of every team game from 1970 to 2013 using the following inputs:

  • The score differential after the first quarter;
  • The score differential after the second quarter;
  • The score differential after the third quarter;
  • The score differential after the fourth quarter;
  • The league average pass/ratio during that season

The best-fit formula to predict pass ratio is:

Pass Ratio = .29% + .046% * 1QM + .076% * 2QM + .195 % * 3QM + .245% * 4QM + 99.5% * LgAvgPassRatio

How does that formula work? Let’s use the Seahawks game against Arizona as an example. In that game, the score was tied after each of the first two quarters, Seattle trailed by 3 after the third quarter, and Arizona won by seven. The league average pass ratio in 2013 was 58.4%, so we would expect Arizona to pass on 56.1% of all plays in a tight game won by the Cardinals. Instead, Arizona passed on just 38.6% of all pass plays. That’s a difference of over seventeen percent. In eleven of Seattle’s 16 games, the opponent passed less frequently than we would expect. And over the course of the season, Seahawks opponents passed nearly six percent less often than we would expect, given the scores in the games. That was the largest differential of 2013. The table below shows the Expected P/R ratio faced (based on the scores after each quarter), the actual P/R ratio seen, and the difference:

Team
Exp P/R Ratio
Act P/R Ratio
Diff
SEA63.157.4-5.74
CHI5752.7-4.33
NWE60.457-3.43
IND59.356.3-2.93
DEN63.760.9-2.84
NOR6159-2.04
KAN61.959.9-1.98
MIA5856.2-1.72
SFO62.761.1-1.62
ATL56.154.6-1.51
STL57.856.6-1.18
TEN57.756.6-1.11
HOU54.353.2-1.11
GNB58.157.4-0.7
BUF57.256.7-0.49
PIT58.658.2-0.37
BAL57.657.4-0.23
TAM56.457.10.7
JAX52.653.40.82
PHI60.361.51.14
DAL58.960.11.17
SDG59.560.81.32
WAS53.955.41.5
CIN61.463.11.68
OAK55.1571.96
CLE56.358.31.96
CAR61.963.92.01
NYG55.758.32.56
DET5961.62.58
NYJ55.459.84.4
MIN55.860.95.06
ARI59.464.55.08

What about historically? I ran the same process for every team season since 1970. Seattle ranks “only” 31st as far as seeing less passes than you would expect, although part of the reason for that is the team’s strong run defense. For example, the number one team, by far, in this metric, was the 2006 Colts. But that year, Indianapolis ranked last in yards per carry allowed. In other words, nobody was passing against Indianapolis that season, but the reason behind it wasn’t a dominant pass defense but a terrible run defense (and maybe a desire to keep Peyton Manning off the field).

Among teams that ranked in the top 10 in yards per carry allowed, Seattle would rank 4th in pass/run ratio differential — behind only the 2007 Colts, 1973 Dolphins, and 1990 Bills.

Rk
Tm
Year
Exp P/R Ratio
Act P/R Ratio
Diff
YPC All. Rk
1IND200657.145.9-11.2532
2MIA198256.146.5-9.5528
3NWE197341.632.7-8.9526
4KAN198850.541.6-8.924
5BUF197842.233.4-8.8728
6IND200762.153.7-8.396
7NWE198149.741.6-8.126
8MIA197349.941.8-8.057
9HOU199452.444.4-7.9823
10BUF197947.539.6-7.8316
11DAL200054.947.3-7.5631
12PHI198349.642.4-7.2518
13BUF199057.850.8-7.046
14MIN199055.148.3-6.8917
15WAS198049.442.6-6.7624
16SEA198250.543.8-6.6927
17MIA200751.344.7-6.6230
18BUF199158.852.2-6.615
19NWE19865750.5-6.4723
20MIA19855750.8-6.2624
21ATL197440.934.7-6.2318
22NYJ200353.747.5-6.1818
23CLE200852.246.1-6.1225
24OAK200651.145-6.0912
25CIN198957.651.7-5.9528
26ATL197245.139.2-5.9314
27BUF201052.646.7-5.9332
28MIA200452.546.6-5.9118
29GNB200553.948-5.8818
30DET197148.742.9-5.817
31SEA201363.157.4-5.747
32CLE201154.148.4-5.7321
33DET197246.140.4-5.723
34OAK201057.952.2-5.723
35CIN199849.343.8-5.5229
36ATL197345.940.4-5.515
37TAM20075953.5-5.497
38NYJ200754.649.1-5.4820
39DAL199561.355.8-5.4818
40IND200357.652.1-5.4724
41SFO197741.636.2-5.462
42MIN19865852.5-5.4610
43NOR197739.133.7-5.4127
44MIA198654.449-5.3927
45DAL199755.350-5.3115
46DEN200754.849.5-5.331
47KAN197543.838.6-5.1826
48BUF197446.441.2-5.1413
49NOR198451.646.5-5.1225
50IND200857.252.1-5.1117

We can also look at the other side of this coin: which teams faced significantly more passes than you would expect? Below are the top 50 teams since 1970. The top team is not much of a surprise: the 2006 Vikings. That year, Minnesota posted the 3rd best YPC allowed average since the merger, and nobody wanted to run against those Vikings. The 1998 Chargers (who allowed the 2nd fewest yards per carry since the merger) also make the list, but the 2000 Ravens do not:

Rk
Tm
Year
Exp P/R Ratio
Act P/R Ratio
Diff
YPC All. Rk
1MIN200652.764.411.651
2RAI198255.163.88.734
3PHI198751.159.17.9813
4PHI199056.664.57.92
5NYJ197946.654.17.53
6NYG198657.464.97.456
7ATL198549.856.97.0926
8TEN200954.361.37.0116
9MIN200757.864.36.582
10MIN199558.965.46.428
11SDG199654.460.86.3823
12MIN199457.864.16.311
13DAL198849.455.66.2316
14TAM201257.363.46.171
15STL197340.946.96.0618
16DAL198354.1605.926
17STL198350.756.65.8814
18SDG19975156.85.88
19NOR19723944.85.7618
20WAS198456.562.25.6819
21DEN197244.349.95.685
22PIT197144.450.15.643
23TEN200756.762.35.6115
24NYG200058.163.75.63
25SDG199851.857.45.61
26SDG200255.661.25.5918
27NOR197043.348.85.5417
28TAM199957.563.15.5116
29WAS201259.364.85.4817
30DET200753.358.85.4623
31WAS198358.6645.417
32DET200950.155.55.4121
33NOR198957.262.65.382
34CLE197643.448.85.3712
35SEA200952.858.25.3613
36SDG197241.546.95.366
37DEN200559.965.15.2215
38CHI201158.263.45.210
39BAL197745.250.45.1924
40SFO200550.255.45.1911
41BAL197050.755.85.1610
42NOR197442.547.65.1415
43PIT198255.560.65.13
44ARI201359.464.55.082
45MIN201355.860.95.0613
46CHI197539.344.24.948
47PHI197144.549.44.9220
48KAN197149.954.94.917
49SDG198256.261.14.8924
50RAM198751.556.44.8921
{ 6 comments }
  • wiesengrund January 26, 2014, 6:46 am

    Intersting thought. I was just wondering, instead of adjusting for good or bad run defense after the fact, maybe it might make sense to include YPC allowed in the regression? After all the decision whether to run or to pass is influenced by the perception of the opponents run defense each and every play, just like it is influenced by the score and the overall passing environment.

    Reply
  • Abel January 26, 2014, 3:29 pm

    I wonder how much this is affected by the opponents they’ve played. The NFC West doesn’t have a reputation for airing it out.

    Reply
    • John January 26, 2014, 4:09 pm

      I’m unsure how true that premise is Abel, but it would likely be offset by the fact the NFC West contained 4 top ten rush defenses.

      Reply
  • Jeremy January 27, 2014, 7:46 pm

    How strong of a regression was this? What was the R^2?

    Reply

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