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Explaining the Power Ranking System

What calculations are made in my NFL Team Ranking system and what attributes to the grades I give on offense, defense, special teams, and schedule?

Brian Spurlock-USA TODAY Sports

Since I debuted the NFL Power Ranking System that takes into account the team stats on offense, defense, special teams, and record of themselves and schedule, everyone has been asking for a detailed explanation of what goes into the calculations. I've had a bit of difficulty trying to figure out how to explain it to myself at times because it's just a collection of random numbers and formulas put together without any context. I will use the 2014 Season numbers as a template to explain what goes into the calculations for those 4 categories. The basic premises is to compare a team's stats against league average and assign a grade based on how better or worse the team is producing compared to league average. So if a team is grading better than 50, that means they are better than league average and if they're below 50, you get the rest.

There's no point in explaining how the system works without using a contemporary example, so I created a spreadsheet for the 2014 season. The 2014 season makes the perfect example to explain the system because the Patriots won the Super Bowl. All the stats are found on the NFL website and Pro Football Reference.

So here's a point by point breakdown detailing each grade:

1. Schedule: Average of Record and Opponent Record Grade

This part of the grade takes into account the team's overall record and the team's opponent records in their other games. An individual grade is assigned to both the team's individual record and their opponent's record in their other games. It rewards teams for winning games, but also punishes teams with an easier opponent schedule.

Tm W L Opp Win Opp Lost Win % Opp Win %
New England Patriots 12 4 127.5 112.5 0.750 0.531
League 256 256 3840 3840 0.500 0.500

*.5 indicates a tie between Carolina and Cincinnati in the 2014 regular season

In the Patriots case, they rate above average in both overall win % and in opponent win % since they played a first place schedule.

The formula for calculating each grade is [(Team % - League %)/(League %)+0.5]*100. The Patriots have a win % of .750 and opponent win % of .531. With .500 being the league average in both categories, you plug in those numbers into a calculator and you get a score of 100 for team record and 56 for opponent record. Then those two numbers are averaged out to a Schedule score of 78. That put the Patriots at 3rd in the NFL in that category behind Seattle and Denver.

2. Offense and Defense: Points Per Drive, Yards Per Play, Turnover %, and Score %

If you haven't heard me say that before, I believe that raw counting stats are BS and do not accurately measure the effectiveness of an offense or defense. A good offense will be able to consistently put up points on each drive, be near the top of the league in yards gained per play, limit turnovers, and score on a lot of their drives. A good defense does the opposite of that. I take it one step further on the Points Per Drive since there is too big a range to cover in the rankings. On offense, I divide points per drive by 7 and on defense divide PPD by 7 and subtract that value from 7 to get an efficiency metric of points allowed.

Team Drives PPD Points Efficiency Plays Yards YPP Turnovers TO % TD FG Scores Score %
Patriots Offense 181 2.40 434 34.3% 1073 5848 5.5 13 7.2% 47 35 82 45.3%
Patriots Defense 182 1.63 297 76.7% 1033 5506 5.3 25 13.7% 30 29 59 32.4%
NFL Offense 5911 1.83 10810 26.1% 32779 178249 5.4 758 12.8% 1189 829 2018 34.1%
NFL Defense 5911 1.83 10810 73.9% 32779 178249 5.4 758 12.8% 1189 829 2018 34.1%

*NFL League Numbers Double Posted just to include defense efficiency

Formula for Off Eff, Off YPP, Off Score %, Def TO %: [(Team-League)/League+0.5]*100
Formula for Def Eff, Def YPP, Def Score %, Off TO %: [(League-Team)/League+0.5]*100

The Patriots offensive grades are 81 for Offensive Efficiency, 50 for Yards Per Play, 95 for Turnover %, and 83 for Score %. Average those four values and the Patriots offense grades at 77. On defense, the grades are 54 for Defensive Efficiency, 52 for Yards Per Play, 57 for Turnover %, and 55 for Score %. That averages to a defensive score of 54 for the Patriots. The Patriots offense ranked 2nd in the NFL and 12th on defense.

3. Special Teams: KR Average, PR Average, TB %, Offensive Field Position, Defensive Field Position, Net Punting, Punt Coverage, Kickoff Coverage

Grading Special Teams is one giant clustertruck, so I won't display the Patriots and the league numbers and instead will just post the averages used in the overall grade. Special Teams grades 8 separate categories and there is not enough space to post all of them.

Team Off Field Def Field Net Punt KR PR Kick Cov Punt Cov TB %
Patriots 30.6 25.5 39.9 22.4 10.5 21.2 9.2 54%
League 27.9 27.9 39.4 23.8 8.9 23.8 8.9 50%

Formula for Off Field, Net Punt, KR, PR, TB %: [(Team-League)/League+0.5]*100
Formula for Def Field , Kick Cov, Punt Cov: [(League-Team)/League+0.5]*100

So for the Patriots the individual grades on Special Teams would be 60 for Offense Field Position, 59 for Defense Field Position, 51 for Net Punting, 44 for kick returns, 68 for punt returns, 57 for touchbacks, 46 for Punt coverage, and 61 for kickoff coverage. That averages out at 56 for the Special teams unit. That ranks the Patriots 9th in the league in special teams.

4. Team Average and Rankings: Offense, Defense, Special Teams, Schedule

Now that the four individual grades are out, the average of the 4 units are taken to give an overall team grade. Then the 32 teams are ranked according to those averages. The average and standard deviance are taken from the data to establish a group of tiers to rank the teams and their individual components. For the 2014 season, the average was 50, the standard deviance was 10, and the median was 51.

Tier Range Color
Great 71-100 Light Blue
Good 60-71 Green
Average 50-60 Yellow
Bad 39-50 Orange
Awful 0-39 Bad

After ranking these teams by their averages, the Patriots finished #1 in the rankings, just narrowly finishing ahead of the Green Bay Packers. The 2014 team scored a 66 in the rankings, which is in the good tier. I believe that the Patriots early season struggles hurt them in that area as well, as they looked like a great team during Weeks 5-16. The same formulas are used for the 2015 Spreadsheet. The numbers are different for 2015 because the sample size is smaller and still subject to change whereas the 2014 numbers are in stone.

For fun, here's how the Super Bowl teams were ranked:

Rank Team Offense Defense Schedule Sp. Teams Average
1 New England Patriots 77 54 78 56 66
3 Seattle Seahawks 71 64 79 44 64

If this is still confusing, please let me know where you're getting lost at. The system itself only measures what each team has produced so far and has no predictive capabilities other than trying to figure out playoff teams from the pack.