One of the fallacies that bugs me in the NFL is the definition of the top offense and defense in the NFL. Generally, the majority of NFL fans and analysts go by yards per game. Defensively speaking, if your team gives up the least yards per game you are crowned the best defense in the league. It gives a simplistic view of offense and defense, but it is incredibly inaccurate and completely ignores millions of dependent variables like time of possession, points, yards per play, etc. Therefore, I decided I wanted to take a deeper look into NFL defenses and find the best one based on more than just yards per game. I will try to take into account those many dependent variables, but remember this is not perfect science (what is really?). This is just one man's statistical review of the issue. I guarantee you though, it is a better representation of a defense as a whole than yards per game.
All of my numbers have been collected from Pro-Football-Reference (and a few other sources listed elsewhere).
Just for reference, below is a table showing yards per game final 2010 statistics. Also, I included points per game, because it is another number that is referenced a lot, but has more weight in my opinion. I color coded the rankings for your visual satisfaction. And, I found an awesome javascript that should allow you to sort the tables per column by clicking on each column header.
| Team | Total Y/G | Y/G Rank | Pass Y/G | PY/G Rank | Rush Y/G | RY/G Rank | Pts/G | Pts/G Rank |
| Chargers | 271.6 | 1 | 177.8 | 1 | 93.8 | 4 | 20.1 | 10 |
| Steelers | 276.8 | 2 | 214.1 | 12 | 62.8 | 1 | 14.5 | 1 |
| Jets | 291.5 | 3 | 200.6 | 6 | 90.9 | 3 | 19 | 6 |
| Saints | 306.3 | 4 | 193.9 | 4 | 112.3 | 16 | 19.2 | 7 |
| Packers | 309.1 | 5 | 194.2 | 5 | 114.9 | 18 | 15 | 2 |
| Dolphins | 309.3 | 6 | 209.3 | 8 | 100.1 | 7 | 20.8 | 13 |
| Giants | 311.9 | 7 | 210.6 | 10 | 101.3 | 8 | 21.7 | 17 |
| Vikings | 312.6 | 8 | 210.4 | 9 | 102.2 | 9 | 21.8 | 18 |
| Bears | 314.3 | 9 | 224.3 | 20 | 90.1 | 2 | 17.9 | 4 |
| Ravens | 318.9 | 10 | 224.9 | 21 | 93.9 | 5 | 16.9 | 3 |
| Raiders | 322.8 | 11 | 189.2 | 2 | 133.6 | 29 | 23.2 | 20 |
| Eagles | 327.2 | 12 | 216.8 | 14 | 110.4 | 15 | 23.6 | 21 |
| 49ers | 327.8 | 13 | 231.1 | 24 | 96.7 | 6 | 21.6 | 16 |
| Chiefs | 330.2 | 14 | 219.9 | 17 | 110.3 | 14 | 20.4 | 11 |
| Bengals | 332 | 15 | 216.8 | 15 | 115.2 | 19 | 24.7 | 24 |
| Falcons | 332.4 | 16 | 226.6 | 22 | 105.9 | 10 | 18 | 5 |
| Buccaneers | 332.7 | 17 | 201 | 7 | 131.7 | 28 | 19.9 | 9 |
| Panthers | 335.9 | 18 | 212.1 | 11 | 123.8 | 23 | 25.5 | 26 |
| Rams | 336.8 | 19 | 223.6 | 19 | 113.1 | 17 | 20.5 | 12 |
| Colts | 341.6 | 20 | 214.6 | 13 | 127 | 25 | 24.3 | 23 |
| Lions | 343.6 | 21 | 218.6 | 16 | 124.9 | 24 | 23.1 | 19 |
| Browns | 350.1 | 22 | 220.7 | 18 | 129.4 | 27 | 20.8 | 14 |
| Cowboys | 351.8 | 23 | 243.4 | 26 | 108.4 | 12 | 27.3 | 31 |
| Bills | 361.6 | 24 | 192 | 3 | 169.6 | 32 | 26.6 | 28 |
| Patriots | 366.5 | 25 | 258.5 | 30 | 108 | 11 | 19.6 | 8 |
| Titans | 367.7 | 26 | 252 | 29 | 115.7 | 20 | 21.2 | 15 |
| Seahawks | 368.6 | 27 | 249.6 | 27 | 118.9 | 21 | 25.4 | 25 |
| Jaguars | 371.8 | 28 | 250.3 | 28 | 121.6 | 22 | 26.2 | 27 |
| Cardinals | 373.6 | 29 | 228.4 | 23 | 145.2 | 30 | 27.1 | 30 |
| Texans | 376.9 | 30 | 267.5 | 32 | 109.4 | 13 | 26.7 | 29 |
| Redskins | 389.3 | 31 | 261.7 | 31 | 127.6 | 26 | 23.6 | 22 |
| Broncos | 390.8 | 32 | 236.3 | 25 | 154.6 | 31 | 29.4 | 32 |
| Avg Team | 336.1 | -- | 221.6 | -- | 114.5 | -- | 22.1 | -- |
From that table we could deduce that the Chargers and Steelers are tied for the best defenses. Each of them ranks at a 4 when the four categories are averaged. Just behind them is the Jets at 4.5, Packers at 7.5, and Saints at 7.8. In dead last, is your the Broncos with a average rank of 30th. Ouch!
However, like I said above, yards per game is relatively pointless, especially when you break it down between rush yards and passing yards. I have stated all year that the Steelers see a lot of teams abandon the run and try to pass, which results in them seeing more pass attempts per game than any other team. That results in them seeing more pass yards, which does not necessarily mean their pass defense is as bad as it ranks in yards per game. Also, when you rank defenses like that you are essentially ruling that turnovers, sacks, and the other important defensive categories are worthless. Moreover, yards per game allowed on defense can be heavily skewed by a team like the Patriots, that dominates time of possession due to their high-powered offense.
I am getting ahead of myself though. A step forward would be looking at the amount of yards a team gives up per play. This is better representation of a defense because it takes in to an account a defense that may see more snaps than another team. If a team has a bad offense, obviously their defense is going to be on the field more. That means they will likely allow more total yards, but could still be playing effective defense. Let me explain a little more after I show you the numbers. The passing numbers will be in yards per attempt, which does not take into account sacks.
| Team | Y/P | Y/P Rk | P Y/A | P Y/A Rk | R Y/A | R Y/A Rk |
| Steelers | 4.5 | 1 | 6.3 | 1 | 3 | 1 |
| Chargers | 4.6 | 2 | 6.4 | 2 | 3.7 | 6 |
| Jets | 4.8 | 3 | 6.5 | 5 | 3.6 | 3 |
| Dolphins | 5 | 4 | 7.1 | 19 | 3.6 | 4 |
| Bears | 5 | 5 | 6.6 | 8 | 3.7 | 5 |
| Packers | 5.1 | 6 | 6.5 | 6 | 4.7 | 28 |
| Vikings | 5.1 | 7 | 6.7 | 9 | 3.9 | 9 |
| Giants | 5.1 | 8 | 6.8 | 10 | 4.2 | 14 |
| Panthers | 5.1 | 9 | 6.9 | 14 | 3.9 | 10 |
| Chiefs | 5.1 | 10 | 6.5 | 7 | 4.3 | 18 |
| Ravens | 5.1 | 11 | 6.4 | 3 | 3.9 | 7 |
| 49ers | 5.1 | 12 | 7.2 | 23 | 3.5 | 2 |
| Raiders | 5.2 | 13 | 7.1 | 20 | 4.5 | 24 |
| Saints | 5.2 | 14 | 6.8 | 11 | 4.3 | 17 |
| Eagles | 5.2 | 15 | 7 | 18 | 4.2 | 15 |
| Titans | 5.2 | 16 | 6.9 | 15 | 3.9 | 8 |
| Rams | 5.3 | 17 | 6.8 | 12 | 4.5 | 22 |
| Bills | 5.4 | 18 | 6.9 | 16 | 4.8 | 32 |
| Buccaneers | 5.4 | 19 | 6.4 | 4 | 4.7 | 29 |
| Colts | 5.4 | 20 | 6.8 | 13 | 4.6 | 27 |
| Browns | 5.4 | 21 | 7.3 | 25 | 4.1 | 12 |
| Lions | 5.5 | 22 | 7.3 | 26 | 4.5 | 23 |
| Cardinals | 5.5 | 23 | 7.3 | 27 | 4.4 | 21 |
| Seahawks | 5.5 | 24 | 7.2 | 24 | 4.2 | 16 |
| Bengals | 5.6 | 25 | 7.1 | 21 | 4.4 | 20 |
| Falcons | 5.6 | 26 | 6.9 | 17 | 4.6 | 25 |
| Patriots | 5.6 | 27 | 7.1 | 22 | 4.2 | 13 |
| Cowboys | 5.8 | 28 | 7.7 | 29 | 4.3 | 19 |
| Broncos | 5.9 | 29 | 7.8 | 30 | 4.7 | 31 |
| Redskins | 5.9 | 30 | 7.5 | 28 | 4.6 | 26 |
| Texans | 6 | 31 | 8.2 | 31 | 4 | 11 |
| Jaguars | 6.3 | 32 | 8.3 | 32 | 4.7 | 30 |
| Avg Team | 5.3 | -- | 7 | -- |
4.2 | -- |
There are a few very good examples of yards per game being very misleading in this table. Take for example the Dolphins pass defense that ranks 8th in yards, but gives up more yards per pass attempt than more than half the league. The reason for that is that all but 3 teams above them in pass yards per game has seen more pass attempts. Therefore, you can see why yards per play is a better ranking system than yards per game. The big surprise for me is how far down that list the Falcons and Patriots rank, the two #1 seeds in the playoffs.
The average ranks in yards per play puts the Steelers at first with a perfect ranking. Following them are the Chargers (3.3), Jets (3.7), Bears (6), and Ravens (7). In dead last is the Jaguars with an average rank of 31.3. And this team almost made it into the playoffs? Yikes.
That's it for part 1 of the analysis. In the next portion we will look into several key defensive numbers like sacks, turnovers, touchdowns allowed, etc. Look for Part 2 tomorrow only on Behind The Steel Curtain.