JP Power Rankings

A few years ago, I realized that the rankings for "total offense" and "total defense" were pretty useless because (a) they were solely based on yards, and (b) they were highly schedule-dependent. At the time, I made a spreadsheet to determine who really had the best offense and defense. I've since forgotten and lost the spreadsheet, but I decided to do the same now.

There are six components to the rating. The first is just won-lost record. It's weighted 20%, so that an unbeaten team gets 20 points and a winless team gets 0 points. The rest are all "adjusted" for opponents and to a 0-1 scale (see below). They are 20% strength-of-performance, 20% points-for, 20% points-against, 10% yards-for, 10% yards-against. The thinking here is that wins are the most important but are not really "robust"; each game is (with limited exception) either a 1 or a 0. So wins count 40%. Points are more important than yards, but yards still tell a useful story.

These six statistics are then summed to form four different rankings. The first is the POWER RANKING, which is how the table is sorted. It is the overall strength measure. The next two are OFFENSE and DEFENSE, while the last is NATURAL. The natural ranking does not use the yard calculations. Here are the formulas for each:

Power = 20*R + 20*S + 20*APF + 20*APA + 10*AYF + 10*AYA
Offense = 20*APF + 10*AYF
Defense = 20*APA + 10*AYA
Natural = 10*S + 10*APF + 10*APA

The last three are all on a 0-30 scale.

Ranking after Week 14 of the 2009 season

Rank Team +/- W L Power Offense Rk Defense Rk Natural Rk
1 Indianapolisnc 130 86.53 21.74 24.84 27.01
2 New Orleansnc 130 82.88 30.01 14.723 24.92
3 Minnesotanc 112 74.94 22.93 20.111 22.44
4 New Englandnc 85 73.36 23.92 24.66 22.83
5 Green Bay+2 94 66.16 18.86 22.28 18.810
6 Baltimore+4 76 65.67 18.510 25.73 21.15
7 San Diego+4 103 65.02 19.87 15.918 20.06
8 Denver-3 85 64.90 13.418 26.82 19.78
9 Philadelphia-1 94 64.80 20.26 18.614 19.77
10 Cincinnati-4 94 62.99 12.518 24.75 19.19
11 Dallas-2 85 62.20 17.511 21.99 18.512
12 NY Jets+2 76 61.45 11.419 30.01 18.711
13 NY Giantsnc 76 57.45 20.45 15.720 16.117
14 Arizona-2 85 56.55 15.813 17.215 18.113
15 Houston+2 67 54.06 18.59 16.816 16.815
16 Miaminc 76 53.11 15.315 16.017 16.616
Rank Team +/- W L Power Offense Rk Defense Rk Natural Rk
17 Pittsburgh-2 67 49.98 14.516 19.312 14.519
18 San Francisco+1 67 49.92 9.323 22.87 17.214
19 Atlanta-1 67 48.81 15.614 15.222 15.918
20 Tennessee+2 67 47.19 17.412 11.527 14.020
21 Jacksonville-1 76 43.81 10.020 14.224 12.721
22 Carolina-1 58 41.12 8.624 19.013 12.422
23 Chicagonc 58 38.86 9.421 15.919 11.923
24 Washington+1 49 37.67 7.026 21.510 11.125
25 Seattle-1 58 34.36 9.322 11.725 10.726
26 Buffalonc 58 33.24 4.829 15.421 11.224
27 Oaklandnc 49 24.25 1.532 11.626 8.127
28 Kansas Citync 310 19.02 5.827 5.531 6.529
29 Cleveland+3 211 18.14 2.730 10.428 7.028
30 Tampa Bay-1 112 17.29 5.428 10.329 5.130
31 Detroit-1 211 13.19 8.425 0.032 3.431
32 St. Louis-1 112 11.41 2.131 7.730 2.732
Rank Team +/- W L Power Offense Rk Defense Rk Natural Rk

Highlighting key
Gold: Top 5 of main ranks or above 75; top 3 of sub ranks or above 25
Purple: Bottom 5 of main ranks or below 25; bottom 3 of sub ranks or below 5
Green: Moved up 3 or more spots; bold indicates best climber
Red: Moved down 3 or more spots; bold indicates worst faller

How the Rankings are Made

Here's what I mean by "adjusted". After 5 weeks of the 2009 season (when these rankings were first published), the Jets had allowed 304.8 yards per game; the Eagles 272.3ypg. Which has the better defense? Not necessarily Philadelphia. The Jets' opponents had averaged 360.2ypg, this means the Jets did 55.4 yards better than average. The Eagles' opponents had averaged merely 309.6, so they did only 37.3 better than average. Thus, "adjusted", the Jets had a better defense than Philadelphia.

To incorporate this into the rankings, though, I need to scale these numbers. I've decided that the best way to do this is a top-to-bottom scale. The Giants were 80.2 yards better than average, the best in the league, so they get 1.000 on this ranking. The Texans were 64.6 yards worse than average, the worst in the league, so they get a 0.000, and all the other teams are scored linearly. Mathematically, this is done as (Score-Min)/(Max-Min). So the Jets get 55.4 - (-64.6) / 80.2 - (-64.6) = 120.0/144.8 = 0.829. The same thing is done with PF, PA, and YF.

What I mean by "strength-of-performance" is a combination of record and SOS, based on the same principle. San Francisco was 3-2 against opponents that averaged a .530 winning percentage. Since a team that played a .530 team would be expected to perform at .470, the 49ers were .130 better than average. Baltimore was 3-2 against opponents that averaged a .420 winning percentage, so they were only .020 better than average. These numbers are scaled 0.000-1.000 in the same way as the points and yards stats. Equivalently, one can add winning percentage and opponents' winning percentage and scale that 0-1. The first stat, record, is not scaled, so if no team has an undefeated record, no team will receive a 1.000 on this scale.

Table of Past Performance

On the left are teams' ratings in past weeks. Dark green is above 70, light green above 50; dark red is below 30, light red is below 50. On the right is teams' ranks in past weeks. Dark green indicates a jump of 3+ spots, dark red a fall of 3+ spots.