Blog Entry

## The 2009 NFL Regular Season In Analytical Review

Posted on: January 4, 2010 11:26 pm
Edited on: January 5, 2010 10:39 pm

A few years back I concocted a system for determining any given level of play, using both their record (winning percentage) and average margin of victory, modified by their opponents' statistics in the same factors.  I tend to disregard other stats - the goal of a team is to win the game, and of all statistics, only points scored and points allowed has a 100% direct correlation to victory - you can't win if you're outscored.  This basically narrows a team down to factors in scoring output and scoring prevention.  I also came up with a formula for determining how significant a home field advantage a team is showing, again using modifiers for scoring output and scoring prevention.

The ratings that result are a sort of mean performance in the stated area, and give a theoretical score based on both teams performing to their consistently displayed ability.  A team's projected offensive score on a neutral site is given by this formula (average NFL score being 21.47 points):

Projected score = Average league score + Team A's Off Rat + Team B's Def Rat

Now if a game is being played on a Team A's home field (as is the case the vast majority of the time), the above formula is modified thusly (average NFL home field adjustment is 2.55 points):

Final Projected Score = Projected Score + (League HFA / 2) + Team A's Off HFA - Team B's Def HFA

Note home field adjustments are added to the home team, and subtracted from the visiting team.

Therefore, the best teams have a positive value for Off Rat and a negative value for Def Rat.  Positive net HFA values indicate a team plays better at home than on the road in comparison with the rest of the league, while negative HFA values indicate playing better on the road than at home.

As the next step in the analysis, a projected result for each game played in the NFL is calculated and compared to the actual result, giving an error variation as far as the projected margins.  For example, the retroactive projection for the 11/2 New Orleans vs. Atlanta game was Saints 32.85, Falcons 24.83.  The actual score was Saints 35, Falcons 27, which means the projected margin was 8.02 vs. the actual margin of 8.00 in favor of the Saints, for an error variation of 0.02.  On the opposite extreme, the retroactive projection for the 10/11 matchup between Jacksonville and Seattle was Seahawks 18.76, Jaguars 15.41 for a 3.35 margin, while the actual score was Seahawks 41, Jaguars 0, for an error variation of 41.00 - 3.35 = 37.65.

The frequency of these error margins are then calculated, and these frequencies used to determine how often a favorite wins depending on the projected margin.  For space reasons, I'll simply include a summary of all possible records and corresponding margins below:

08-08 record (050.00% WP):  00.00 margin
09-07 record (056.25% WP):  02.33 margin
10-06 record (062.50% WP):  04.18 margin
11-05 record (068.75% WP):  06.48 margin
12-04 record (075.00% WP):  08.09 margin
13-03 record (081.25% WP):  10.31 margin
14-02 record (087.50% WP):  14.65 margin
15-01 record (093.75% WP):  18.92 margin
16-00 record (100.00% WP):  37.65 margin

The various winning percentages are then summed up for each team, giving them a projected winning percentage, projected PF (points for) and PA (points against).  As a side note, the retroactive projections correctly produced the winner 77% of the time.  Upsets do happen, and the best team doesn't always win.

All that explained, here's a listing of all NFL teams, from best to worst according to the ratings, as well as simulated vs. actual wins and scoring margins, with a brief commentary for each.  The below ratings do not reflect trends - these are mean values throughout the season.

01 New Orleans Saints:  Pow Rat +10.50; Off Rat +11.12; Def Rat +00.62; Pow HFA -00.81; Off HFA -00.86; Def HFA -00.04
Simulations:  WP 79% (vs. 81% actual); +12.00 margin (vs. +10.56 actual); 32.53 PF (vs. 31.88 actual); 20.53 PA (vs. 21.31 actual)
Starters were rested in their last game, which may understate their actual overall ability

02 Indianapolis Colts:  Pow Rat +09.80; Off Rat +06.36; Def Rat -03.45; Pow HFA -02.15; Off HFA -02.40; Def HFA -00.26
Simulations:  WP 79% (vs. 88% actual); +11.23 margin (vs. +06.81 actual); 28.82 PF (vs. 26.00 actual); 17.59 PA (vs. 19.19 actual)
Rested starters their last two games; highly overstated projection in margin balanced by highly understated projection in win %

03 New England Patriots:  Pow Rat +08.91; Off Rat +05.57; Def Rat -03.34; Pow HFA +10.00; Off HFA +05.22; Def HFA -04.78
Simulations:  WP 66% (vs. 63% actual); +07.92 margin (vs. +08.88 actual); 26.06 PF (vs. 26.69 actual); 18.13 PA (vs. 17.81 actual)
Toughest schedule among all playoff teams and HFA adjustments preventing record from being better than the rating would indicate

04 San Diego Chargers:  Pow Rat +08.76; Off Rat +07.50; Def Rat -01.26; Pow HFA -03.74; Off HFA -01.52; Def HFA +02.22
Simulations:  WP 74% (vs. 81% actual); +09.20 margin (vs. +08.38 actual); 28.99 PF (vs. 28.38 actual); 19.79 PA (vs. 20.00 actual)
The ratings may be selling this team short, as projections seem to fall short of the actual results overall

05 Dallas Cowboys:  Pow Rat +07.02; Off Rat +00.36; Def Rat -06.66; Pow HFA +04.72; Off HFA +03.60; Def HFA -01.12
Simulations:  WP 67% (vs. 69% actual); +07.31 margin (vs. +06.94 actual); 23.00 PF (vs. 22.56 actual); 15.69 PA (vs. 15.63 actual)
Lies, damn lies and statistics - yardage rankings and scoring rankings seem to be reversed

06 Minnesota Vikings:  Pow Rat +06.73; Off Rat +06.36; Def Rat -00.38; Pow HFA +05.12; Off HFA +01.83; Def HFA -03.29
Simulations:  WP 73% (vs. 75% actual); +10.14 margin (vs. +09.88 actual); 29.77 PF (vs. 29.38 actual); 19.63 PA (vs. 19.50 actual)
A good team, but the third easiest schedule per these ratings made them look great

07 Philadelphia Eagles:  Pow Rat +06.42; Off Rat +05.97; Def Rat -00.45; Pow HFA +01.79; Off HFA +01.70; Def HFA -00.10
Simulations:  WP 67% (vs. 69% actual); +06.19 margin (vs. +05.75 actual); 27.01 PF (vs. 26.81 actual); 20.82 PA (vs. 21.06 actual)
Very similar ratings to the Vikings, but a more difficult schedule made their record and margin less lofty

08 New York Jets:  Pow Rat +06.38; Off Rat +00.02; Def Rat -06.36; Pow HFA -06.48; Off HFA -03.91; Def HFA -02.57
Simulations:  WP 63% (vs. 56% actual); +05.28 margin (vs. +07.00 actual); 21.01 PF (vs. 21.75 actual); 15.72 PA (vs. 14.75 actual)
Ratings might be overstated due to last two opponents pulling starters; the league's best "road warriors"

09 Green Bay Packers:  Pow Rat +05.61; Off Rat +05.43; Def Rat -00.18; Pow HFA +01.62; Off HFA -00.23; Def HFA -01.86
Simulations:  WP 73% (vs. 69% actual); +09.31 margin (vs. +10.25 actual); 28.78 PF (vs. 28.81 actual); 19.47 PA (vs. 18.56 actual)
Practical twins (if a strong case of sibling rivalry) with the Vikings; aided by high offensive scoring and easy schedule

10 Baltimore Ravens:  Pow Rat +05.16; Off Rat +01.41; Def Rat -03.75; Pow HFA -00.09; Off HFA +00.38; Def HFA +00.47
Simulations:  WP 60% (vs. 56% actual); +04.16 margin (vs. +08.13 actual); 22.37 PF (vs. 24.44 actual); 18.21 PA (vs. 16.31 actual)
Huge discrepancy between winning percentage and average margin makes this team difficult to project accurately

11 Atlanta Falcons:  Pow Rat +04.13; Off Rat +02.25; Def Rat -01.88; Pow HFA -00.08; Off HFA -01.80; Def HFA -01.72
Simulations:  WP 56% (vs. 56% actual); +01.86 margin (vs. +02.38 actual); 22.40 PF (vs. 22.69 actual); 20.55 PA (vs. 20.31 actual)
Fifth most difficult schedule in the NFL greatly hindered their quest for their 2nd playoff berth in a row

12 Carolina Panthers:  Pow Rat +02.90; Off Rat -01.12; Def Rat -04.02; Pow HFA -03.41; Off HFA -02.78; Def HFA +00.64
Simulations:  WP 50% (vs. 50% actual); +00.12 margin (vs. +00.44 actual); 19.72 PF (vs. 19.69 actual); 19.60 PA (vs. 19.25 actual)
Third most difficult schedule and Delhomme's struggles overshadowed a playoff-caliber defense

13 Cincinnati Bengals:  Pow Rat +02.44; Off Rat -01.66; Def Rat -04.10; Pow HFA +00.04; Off HFA -01.71; Def HFA -01.75
Simulations:  WP 57% (vs. 63% actual); +02.73 margin (vs. +00.88 actual); 19.74 PF (vs. 19.06 actual); 17.01 PA (vs. 18.19 actual)
A considerably easier schedule than Carolina's makes Cincy's defense less overshadowed

14 Houston Texans:  Pow Rat +02.37; Off Rat +02.86; Def Rat +00.49; Pow HFA -02.61; Off HFA -00.86; Def HFA +01.74
Simulations:  WP 59% (vs. 56% actual); +03.51 margin (vs. +03.44 actual); 24.69 PF (vs. 24.25 actual); 21.17 PA (vs. 20.81 actual)
Much better on the road than they were last year

15 Pittsburgh Steelers:  Pow Rat +01.76; Off Rat +01.01; Def Rat -00.75; Pow HFA +06.75; Off HFA +04.90; Def HFA -01.85
Simulations:  WP 57% (vs. 56% actual); +02.85 margin (vs. +02.75 actual); 23.33 PF (vs. 23.00 actual); 20.48 PA (vs. 20.25 actual)
Pitt's HFA adjustment may go a long way toward explaining losses to clearly inferior teams on the road

16 Miami Dolphins:  Pow Rat +01.21; Off Rat +02.68; Def Rat +01.46; Pow HFA +01.14; Off HFA +03.60; Def HFA +02.52
Simulations:  WP 46% (vs. 44% actual); -01.91 margin (vs. -01.88 actual); 22.39 PF (vs. 22.50 actual); 24.30 PA (vs. 24.38 actual)
Decent team + hardest schedule in the league - starting RB - 3 quarterbacks = no repeat playoff performance

17 Denver Broncos:  Pow Rat +00.81; Off Rat -00.78; Def Rat -01.58; Pow HFA -01.58; Off HFA -02.21; Def HFA -00.63
Simulations:  WP 55% (vs. 50% actual); +01.82 margin (vs. +00.13 actual); 20.83 PF (vs. 20.38 actual); 19.00 PA (vs. 20.25 actual)
The projections exceed the actual performance more than any other NFL team; probably a bit overrated here

18 Arizona Cardinals:  Pow Rat +00.78; Off Rat +00.67; Def Rat -00.11; Pow HFA -04.28; Off HFA -01.46; Def HFA +02.82
Simulations:  WP 58% (vs. 63% actual); +03.51 margin (vs. +03.13 actual); 24.26 PF (vs. 23.44 actual); 20.75 PA (vs. 20.31 actual)
NFL's easiest schedule + average team = division champions; average division champion + negative HFA adjustment = early exit in playoffs

19 New York Giants:  Pow Rat +00.68; Off Rat +04.91; Def Rat +04.23; Pow HFA +01.84; Off HFA +02.74; Def HFA +00.90
Simulations:  WP 48% (vs. 50% actual); -01.27 margin (vs. -01.56 actual); 25.33 PF (vs. 25.13 actual); 26.60 PA (vs. 26.69 actual)
Don't blame Eli Manning for the team's decline - his brother Peyton would have difficulty winning with the Giants' defense

20 Tennessee Titans:  Pow Rat -00.66; Off Rat +01.90; Def Rat +02.56; Pow HFA +00.28; Off HFA +01.62; Def HFA +01.34
Simulations:  WP 42% (vs. 50% actual); -02.92 margin (vs. -03.00 actual); 21.74 PF (vs. 22.13 actual); 24.66 PA (vs. 25.13 actual)
The ratings might be selling this team short, possibly as a result of the impact the 59-0 loss to the Patriots had on the margin

21 San Francisco 49ers:  Pow Rat -00.98; Off Rat -03.45; Def Rat -02.48; Pow HFA -00.43; Off HFA -01.16; Def HFA -00.73
Simulations:  WP 53% (vs. 50% actual); +1.52 margin (vs. +3.06 actual); 19.57 PF (vs. 20.63 actual); 18.04 PA (vs. 17.56 actual)
The NFC West might have bloated their record a bit, but the defensive foundation is there

22 Buffalo Bills:  Pow Rat -02.39; Off Rat -04.81; Def Rat -02.42; Pow HFA -00.39; Off HFA -01.75; Def HFA -01.36
Simulations:  WP 38% (vs. 38% actual); -4.53 margin (vs. -04.25 actual); 16.10 PF (vs. 16.13 actual); 20.63 PA (vs. 20.38 actual)
The defense is good, but they need to develop a quarterback and stick with him

23 Chicago Bears:  Pow Rat -03.90; Off Rat -01.89; Def Rat +02.01; Pow HFA +02.20; Off HFA +02.23; Def HFA +00.03
Simulations:  WP 43% (vs. 44% actual); -02.68 margin (vs. -03.00 actual); 19.99 PF (vs. 20.44 actual); 22.67 PA (vs. 23.44 actual)
Some patience might be in order; let's see if Cutler continues to adjust and measure the impact of Urlacher's return

24 Jacksonville Jaguars:  Pow Rat -04.37; Off Rat -02.78; Def Rat +01.59; Pow HFA +01.25; Off HFA +01.48; Def HFA +00.24
Simulations:  WP 37% (vs. 44% actual); -05.18 margin (vs. -05.63 actual); 17.72 PF (vs. 18.13 actual); 22.89 PA (vs. 23.75 actual)
Another team that might be sold short here, but that scoring margin rarely equates to a true playoff-caliber team

25 Washington Redskins:  Pow Rat -07.01; Off Rat -06.74; Def Rat +00.27; Pow HFA -03.46; Off HFA -03.09; Def HFA +00.37
Simulations:  WP 31% (vs. 25% actual); -07.13 margin (vs. -04.38 actual); 15.06 PF (vs. 16.63 actual); 22.19 PA (vs. 21.00 actual)
No single high-priced acquisition is going to fix the multiple holes on offense

26 Tampa Bay Buccaneers:  Pow Rat -07.54; Off Rat -05.53; Def Rat +02.01; Pow HFA -03.33; Off HFA -00.55; Def HFA +02.78
Simulations:  WP 22% (vs. 19% actual); -10.89 margin (vs. -09.75 actual); 14.42 PF (vs. 15.25 actual); 25.31 PA (vs. 25.00 actual)
Did about as well as a rebuilding team with the league's second toughest schedule could

27 Cleveland Browns:  Pow Rat -07.72; Off Rat -05.69; Def Rat +02.03; Pow HFA +00.98; Off HFA -01.15; Def HFA -02.13
Simulations:  WP 31% (vs. 31% actual); -07.20 margin (vs. -08.13 actual); 15.81 PF (vs. 15.31 actual); 23.00 PA (vs. 23.44 actual)
A schedule that was tougher earlier than later made many think the team was worse than it actually was at the beginning

28 Oakland Raiders:  Pow Rat -08.04; Off Rat -07.55; Def Rat +00.48; Pow HFA -02.52; Off HFA -01.40; Def HFA +01.12
Simulations:  WP 23% (vs. 31% actual); -10.51 margin (vs. -11.38 actual); 13.12 PF (vs. 12.31 actual); 23.62 PA (vs. 23.69 actual)
Mystifying combination of giant-killer mentality and face-planting against equal or inferior opposition

29 Kansas City Chiefs:  Pow Rat -08.51; Off Rat -02.52; Def Rat +05.99; Pow HFA -05.56; Off HFA -02.25; Def HFA +03.31
Simulations:  WP 29% (vs. 25% actual); -07.93 margin (vs. -08.13 actual); 18.32 PF (vs. 18.38 actual); 26.25 PA (vs. 26.50 actual)
Considering how Kansas City was a feared road trip just a few years ago, the net HFA rating comes as a bit of a shock

30 Seattle Seahawks:  Pow Rat -09.19; Off Rat -04.89; Def Rat +04.30; Pow HFA +04.38; Off HFA -00.44; Def HFA -04.82
Simulations:  WP 36% (vs. 31% actual); -07.40 margin (vs. -06.88 actual); 16.79 PF (vs. 17.50 actual); 24.20 PA (vs. 24.38 actual)
Equally bad on both sides of the ball - major rebuilding project

31 Detroit Lions:  Pow Rat -14.69; Off Rat -05.33; Def Rat +09.36; Pow HFA +00.03; Off HFA +01.09; Def HFA +01.06
Simulations:  WP 17% (vs. 13% actual); -14.67 margin (vs. -14.50 actual); 15.90 PF (vs. 18.38 actual); 30.57 PA (vs. 30.88 actual)
No longer sure if they are better than last year or just luckier to get two wins against bad opposition

32 St. Louis Rams:  Pow Rat -17.40; Off Rat -11.64; Def Rat +05.75; Pow HFA -01.22; Off HFA +01.09; Def HFA +02.31
Simulations:  WP 13% (vs. 06% actual); -16.44 margin (vs. -16.31 actual); 11.27 PF (vs. 10.94 actual); 27.71 PA (vs. 27.25 actual)
One of the worst teams of all time; only the '87 Falcons and the '81 Colts are worse teams by these calculations

For the most part, the simulated values are given as a sort of validation for the accuracy of the ratings, and as noted above, they will not be able to accurately account for games where a team deliberately fails to play a team to its fullest potential (such as teams resting starters for the playoffs, or other teams taking advantage of those backups).
Category: NFL