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The Toolbox: Defensive PPP

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By Bill C. Updated
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Yesterday, we looked at college football's most explosive offenses.  Today, we look at which defenses are best at preventing explosiveness.  But first, here's a question asked in comments yesterday:

[W]hat Im semi curious of is does it take into account what down the play was on. Because given a scenario like FSU vs UF 2003, PK Sam’s bomb of a catch was great and was what scored the winning touchdown, but the 4th down conversion the play before made those points possible. So essentially what I mean is that the 24 yards Dominic Robinson got should count just as much as the 52 yard bomb that PK Sam caught. I understand it wasn’t as explosive, but without the conversion on 4th, the 52 yards bomb never happens.

So what I’m really wondering is how would you be able to combine the success rate into the epp and generate an importance per play of a drive.

This was something I covered in Varsity Numbers a couple of years ago.

The concept behind EqPts is a simple one. Each yard line has a point value assigned to it based on the number of points an offense can expect to score in a possession involving a play from that yard line. The 20-yard line is worth 1.179 EqPts. The opposing 20-yard line is worth 3.898. Each play is assigned a point value based on where the play started and where it finished. The slope is different throughout the field. A gain of five yards from your 20 to your 25 is worth 0.064 EqPts. From the opponent's 40 to the opponent's 35: 0.441 EqPts. From the opponent's 10 to the opponent's 5: 0.582 EqPts. The concept of EqPts is intended to give more weight to more important gains.

Second- and third-level EqPts are in essence derivatives of the EqPts concept. Second-level EqPts take two factors into account: yard line and down. First down from your 20 (1.488) has a different point value than third down from your 20 (0.808). Another example: First down from the opponent's 10 is worth 4.881 EqPts, second down is worth 4.477, and third down is worth 3.818. It's not a hard concept to explain; the points you can expect to score go down as the down markers go up.

With second-level EqPts, a play can have a negative value without losing yards. As mentioned in the quote above, second-level EqPts don't tie as closely to actual point values (because of the possibility of negative values, the sum of all second-level EqPt values is only about 82 percent of the sum of first-level EqPts), but looking at second-level Points Per Play (or 2ndPPP) adds a factor of timely play-making to the equation -- because in football, as in comedy and sniper-fire, it's all about timing -- while further subtracting empty gains on second- or third-and-long.

The 2ndPPP concept is not one that I've pursued in great detail, and for two main reasons: 1) I need more hours in the day, and 2) its correlation to overall quality is lower than that of PPP.  For a while, I was combining PPP and 2ndPPP for the 'P' portion of S&P+, but the correlations just did not support it.  I think there is value in 2ndPPP (and 3rdPPP, which takes into account down and distance), but it is as much contextual as evaluative.  For every interesting observation you can make (the ten highest 2ndPPP averages from 2005-10 all happened in 2008), you can make a nonsensical one (the top 2010 offense according to 2ndPPP: New Mexico).  Put this on the long-term, "need to look into this" list.

Now, to Defensive PPP.  We start with the same anchors as always.

Worst Single-Season Defensive PPP, 2005-10
1. North Texas (2008): 0.61
2. UNLV (2010): 0.54
3. New Mexico State (2010): 0.51
4. Eastern Michigan (2010): 0.51
5. Eastern Michigan (2008): 0.50
6. Utah State (2006): 0.49
7. Temple (2006): 0.49
8. Washington State (2009): 0.49
9. Rice (2005): 0.48
10. Rice (2007): 0.47

Other Teams of Note
13. Washington State (2008): 0.47
17. Washington (2008): 0.47
21. Iowa State (2008): 0.46
22. Minnesota (2010): 0.46
32. Washington State (2010): 0.45

Again, there is no faking PPP.  There are many different ways to become efficient -- Wake Forest's Jim Grobe mastered the art of misdirection for the Demon Deacons for a few seasons -- but there is only one way to be explosive over the course of a full season; 1a) be fast, 1b) get into the open field a lot.  Defensively, then, there is only one way to allow a ridiculously high PPP: 1a) don't be fast, 1b) allow teams into the open field a lot.  Therefore, there are few surprises on this list.  The teams with the worst overall Def. PPP are the slow mid-major defenses who give up a ton of big plays.  The BCS teams on the extended list are the same.

(And once again, 2009 Washington State makes an appearance. Right after I write my "How 2ndPPP Proves that 2008 Was the Greatest Offensive Season of All-Time" book, I'll write my "What Special Confluence of Events Caused a Major Conference Team to Be as Bad as 2009 Wazzu" book.)

Best Single-Season Defensive PPP, 2005-10
1. Virginia Tech (2006): 0.17
2. Nebraska (2009): 0.18
3. Miami (2005): 0.19
4. Florida (2009): 0.19
5. USC (2008): 0.19
6. TCU (2009): 0.19
7. TCU (2006): 0.19
8. Alabama (2009): 0.19
9. Iowa (2009): 0.19
10. Ohio State (2009): 0.19

Other Teams of Note
11. Penn State (2009): 0.19
12. Penn State (2005): 0.20
13. West Virginia (2010): 0.20
14. Boston College (2005): 0.20
15. Ohio State (2006): 0.20

Lots of 2009 on that list.  If 2008 was A New Offensive Hope episode of the Spread Wars trilogy, 2009 was The Defense Strikes Back.  (The Jar Jar Binks in this weak Star Wars analogy?  Barry Switzer.  I don't have to explain myself.)

While TCU makes appearances on both the PPP and Success Rates lists, as a whole, comparing teams' success rates to PPP give you an interesting clue into their identity.  Teams like Boston College, Iowa and Penn State try to prevent big plays and force you to run as many plays as possible to score (wagering that you cannot, in fact, do that).  Meanwhile some other teams -- in 2010, good examples appear to be Oklahoma, Texas and Miami -- attack a bit more and try to keep success rates low while risking a big play or two.

So here is your list of 2010 defenses, ranked in order of opponent-adjusted PPP+ (which, as always, we will explore in the future):

2010 FBS Defenses, Ranked by PPP+
Rk Offense ClosePPP+ Raw PPP Rk Rushing PPP Rk Passing PPP Rk
1 Boise State 171.2 0.22 3 0.22 8 0.22 1
2 Ohio State 167.1 0.23 5 0.22 9 0.25 6
3 TCU 158.7 0.21 2 0.19 4 0.23 2
4 Boston College 152.4 0.22 4 0.17 2 0.26 7
5 Notre Dame 149.7 0.28 23 0.28 50 0.27 13
6 West Virginia 145.7 0.20 1 0.16 1 0.23 3
7 Iowa 144.0 0.26 9 0.24 14 0.28 14
8 Alabama 143.6 0.28 21 0.23 11 0.32 36
9 South Carolina 140.7 0.31 45 0.24 12 0.38 68
10 LSU 140.1 0.27 17 0.27 38 0.27 11
11 Stanford 138.2 0.26 10 0.25 25 0.27 10
12 Mississippi State 138.1 0.30 37 0.25 20 0.35 50
13 Oregon 133.0 0.27 19 0.24 17 0.30 27
14 Nebraska 132.6 0.24 6 0.24 19 0.23 4
15 Wisconsin 132.1 0.28 24 0.26 35 0.29 23
16 Missouri 132.1 0.26 13 0.28 48 0.24 5
17 Clemson 131.5 0.26 12 0.19 5 0.35 46
18 Texas A&M 130.7 0.28 26 0.25 27 0.31 28
19 Utah 129.0 0.28 22 0.17 3 0.37 65
20 Oklahoma 128.6 0.28 25 0.28 45 0.28 15
21 Miami-FL 128.6 0.29 29 0.29 54 0.28 16
22 Pittsburgh 128.5 0.25 8 0.24 16 0.26 8
23 Illinois 127.6 0.31 44 0.24 13 0.38 70
24 Central Florida 126.8 0.25 7 0.20 6 0.29 17
25 Florida 126.6 0.28 28 0.26 29 0.31 32
26 Oklahoma State 126.5 0.27 18 0.21 7 0.32 34
27 BYU 126.1 0.30 33 0.29 53 0.31 30
28 California 125.4 0.31 52 0.31 69 0.32 35
29 Arizona 124.5 0.31 43 0.27 40 0.35 47
30 Arkansas 124.5 0.32 55 0.30 63 0.34 41
31 Florida State 124.4 0.27 14 0.24 15 0.29 19
32 Maryland 123.2 0.27 16 0.26 32 0.27 12
33 Penn State 122.9 0.32 53 0.27 36 0.38 67
34 Auburn 121.2 0.34 63 0.26 31 0.40 82
35 Georgia 120.6 0.32 54 0.29 59 0.35 54
36 SMU 120.0 0.30 41 0.26 34 0.36 55
37 Oregon State 119.4 0.36 79 0.31 68 0.42 93
38 Texas 119.0 0.29 32 0.30 61 0.29 20
39 Purdue 118.9 0.31 47 0.28 47 0.35 47
40 Michigan State 117.2 0.30 34 0.25 24 0.34 44
41 NC State 117.0 0.29 31 0.26 28 0.33 40
42 USC 115.9 0.34 66 0.32 78 0.37 62
43 Virginia Tech 115.3 0.31 50 0.33 84 0.30 24
44 Arizona State 115.2 0.31 49 0.25 21 0.38 66
45 North Carolina 112.9 0.30 38 0.26 30 0.34 43
46 South Florida 111.4 0.26 11 0.23 10 0.29 21
47 Iowa State 106.2 0.33 60 0.27 44 0.40 81
48 Tennessee 106.2 0.34 62 0.35 98 0.32 37
49 UCLA 106.0 0.36 78 0.36 102 0.36 56
50 Air Force 104.7 0.31 47 0.31 69 0.32 33
51 Connecticut 104.3 0.30 35 0.27 41 0.33 39
52 Hawaii 104.0 0.32 58 0.27 42 0.38 72
53 Vanderbilt 103.7 0.37 86 0.32 79 0.43 96
54 Navy 102.8 0.33 59 0.29 58 0.36 59
55 Toledo 102.4 0.31 46 0.32 83 0.30 25
56 Syracuse 101.6 0.27 20 0.25 22 0.31 31
57 Fresno State 101.0 0.37 88 0.40 113 0.35 49
58 Marshall 100.3 0.32 56 0.29 57 0.35 45
59 Colorado 100.1 0.38 93 0.31 66 0.44 99
60 Louisville 99.7 0.30 40 0.29 52 0.33 38
61 Louisiana Tech 98.5 0.36 81 0.31 67 0.41 89
62 Nevada 98.1 0.31 42 0.31 65 0.31 29
63 San Diego State 98.0 0.30 39 0.25 26 0.36 57
64 Kent State 96.9 0.27 15 0.27 39 0.26 9
65 Ole Miss 96.7 0.39 102 0.32 80 0.45 101
66 Washington 96.6 0.37 89 0.39 108 0.35 52
67 Kentucky 96.1 0.36 85 0.36 103 0.37 63
68 Utah State 94.9 0.38 95 0.37 105 0.39 76
69 Northern Illinois 94.1 0.29 30 0.27 37 0.30 26
70 Southern Miss 94.0 0.34 65 0.31 75 0.36 58
71 Temple 93.5 0.28 26 0.27 43 0.29 22
72 Idaho 92.8 0.35 71 0.34 94 0.37 61
73 UL-Monroe 92.4 0.36 73 0.32 76 0.39 77
74 Texas Tech 91.1 0.36 77 0.32 77 0.39 78
75 Tulsa 90.6 0.36 75 0.28 49 0.42 92
76 Baylor 90.1 0.35 67 0.33 88 0.37 60
77 Northwestern 89.7 0.36 83 0.34 95 0.38 71
78 Florida Atlantic 89.3 0.34 64 0.31 64 0.38 73
79 Wake Forest 88.8 0.38 99 0.34 96 0.42 94
80 Miami-OH 88.8 0.32 57 0.36 101 0.29 18
81 Arkansas State 88.8 0.38 90 0.31 71 0.47 106
82 Army 88.6 0.36 80 0.32 81 0.41 88
83 San Jose State 88.6 0.40 105 0.39 110 0.40 85
84 UAB 88.0 0.36 84 0.31 73 0.41 90
85 Buffalo 87.7 0.33 61 0.26 33 0.43 95
86 Georgia Tech 87.2 0.36 76 0.34 89 0.39 74
87 Duke 87.1 0.38 100 0.31 72 0.49 108
88 Central Michigan 86.9 0.36 74 0.33 86 0.39 75
89 Rutgers 86.3 0.36 72 0.29 55 0.43 97
90 Ohio 86.1 0.30 36 0.24 18 0.35 53
91 Wyoming 85.2 0.38 95 0.31 74 0.48 107
92 Kansas 85.1 0.39 103 0.37 106 0.41 86
93 Michigan 84.7 0.41 109 0.36 100 0.47 104
94 Western Michigan 84.5 0.35 70 0.29 56 0.41 91
95 Florida International 84.5 0.35 69 0.35 99 0.35 51
96 Colorado State 84.2 0.43 110 0.33 87 0.54 115
97 Washington State 84.1 0.45 112 0.45 118 0.44 100
98 Kansas State 83.5 0.38 94 0.37 104 0.39 79
99 Houston 83.2 0.37 87 0.34 91 0.41 87
100 UL-Lafayette 83.0 0.41 108 0.35 97 0.47 105
101 Bowling Green 82.4 0.40 104 0.34 93 0.46 103
102 Western Kentucky 82.0 0.38 98 0.40 112 0.37 64
103 Middle Tennessee 81.3 0.31 51 0.29 60 0.34 42
104 Minnesota 80.7 0.46 116 0.39 109 0.55 116
105 Troy 80.4 0.38 92 0.38 107 0.38 68
106 Tulane 79.4 0.40 107 0.40 114 0.39 80
107 East Carolina 79.4 0.45 114 0.41 116 0.51 111
108 Virginia 79.3 0.40 106 0.40 111 0.40 84
109 Cincinnati 79.1 0.38 97 0.28 46 0.49 109
110 Memphis 77.9 0.46 117 0.34 90 0.59 117
111 North Texas 77.8 0.38 101 0.33 85 0.45 102
112 New Mexico 77.7 0.45 115 0.41 115 0.52 113
113 Rice 77.1 0.45 113 0.30 62 0.59 118
114 UTEP 76.1 0.36 82 0.32 82 0.40 83
115 UNLV 75.2 0.54 120 0.45 119 0.66 120
116 Indiana 75.2 0.43 111 0.34 92 0.52 112
117 Akron 74.8 0.38 91 0.25 23 0.51 110
118 Ball State 73.8 0.35 68 0.28 51 0.43 98
119 New Mexico State 66.5 0.51 119 0.49 120 0.53 114
120 Eastern Michigan 61.0 0.51 118 0.41 117 0.63 119

Though they did something other Boise State teams haven't done -- lose a game -- advanced stats suggest that the 2010 Broncos were Chris Petersen's best team yet.  Thanks to the presence of two undefeated BCS conference teams, BSU almost certainly wouldn't have made the national title game even if they hadn't lost to Nevada via two baffling missed kicks (a shame, as I'm pretty sure they were as good, or very nearly as good, as the two title game participants), but they were potentially the best all-around non-BCS conference team of the "We have play-by-play data for it" era.

(I still need a better name for that.)

By the way ... in said play-by-play era, West Virginia's defense has been fantastic, horrific and fantastic again.  A tough feat.

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