I have finally found something mathematically significant in my now week long study of NFL defenses. It’s not what I was hoping for, but ultimately it might be the best measure for the quality of a defense that we have. I’m going to continue to work with the data to develop a statistical model that fits all the data that I’ve presented over the last week, but I’m now very close to the ultimate defensive analysis tool I was after.
First a recap:
The NFL uses yard allowed to rate defense. We all know this is extremely flawed. Yards allowed doesn’t correlate highly to points allowed, and thus it doesn’t correlate to wins. It’s just a poor measure. I also showed that yards allowed was highly dependent on the # of possessions, which is something the defense has no control over.
The other measurement current used is points allowed. This is especially true for fans of teams like Seattle; a team that was #1 in that category, despite being less than steller in other statical measures. The problem is that this is also dependent on the number of possessions, and I also have shown that it is dependent on the average starting field position for the opponents. Again, these are things that the defense can’t control.
This problem led me to break down the results of each drive by it’s conclusion: touchdowns, punts, etc. The result there was too many variables and nothing to regress that data to. While there was plenty of anecdotal results that were very interesting, there wasn’t anything significant mathematically that could be found at this point.
Recap over. Now on to new results.
This time, looked at something simple: yards per drive. It’s is one of the only factors that the defense has full control over. The better the defense, the quicker they’ll get off the field, right? Sure, there’s the “bend but don’t break” philosophy but while that might be functional, it’s is hardly dominant.
The problem here is that this evaluation of the defensive play doesn’t correlate highly to anything significant, like points given up, or wins. There’s just too many other factors that effect those things we’d want to correlate it to.
To begin to account for that, I took the average starting field position for each defense, and added that to the yards given up to give me the average yard yard where drives ended.
That number, actually correlated quite nicely to points given up. It’s still not perfect, and there’s still one more variable I need to account for (getting turnovers appears to be a big factor), but I think that I may have stumbled on to something that is very mathematically significant.
Unfortunately, it’s very late here, so that’s going to have to wait until tomorrow. I will say that once I account for turnovers, i believe I’ll end up showing that yards per drive is an extremely accurate indicator of how well a defense played.
Until then, I’ll just leave you with today’s data:
|Rk||Team||yards/dr||Rk||Team||ave drive end|
|1||Denver Broncos||25.01||1||Denver Broncos||49.24|
|2||Pittsburgh Steelers||25.36||2||San Francisco 49ers||47.87|
|3||Chicago Bears||26.30||3||Chicago Bears||47.75|
|4||Arizona Cardinals||26.37||4||Cincinnati Bengals||47.04|
|5||Houston Texans||26.39||5||Arizona Cardinals||45.97|
|6||San Francisco 49ers||27.23||6||Seattle Seahawks||45.93|
|7||Cincinnati Bengals||27.50||7||Houston Texans||45.63|
|8||New York Jets||27.67||8||Pittsburgh Steelers||44.77|
|9||Green Bay Packers||29.28||9||Green Bay Packers||44.76|
|10||Detroit Lions||29.50||10||San Diego Chargers||44.19|
|11||Baltimore Ravens||29.55||11||New York Jets||43.94|
|12||San Diego Chargers||29.68||12||Baltimore Ravens||43.43|
|13||Seattle Seahawks||29.87||13||New England Patriots||43.13|
|14||Cleveland Browns||30.01||14||Cleveland Browns||42.85|
|15||Minnesota Vikings||30.94||15||Minnesota Vikings||41.80|
|16||St. Louis Rams||31.15||16||Atlanta Falcons||41.67|
|17||Philadelphia Eagles||31.20||17||Tampa Bay Buccaneers||41.08|
|18||New England Patriots||31.27||18||Detroit Lions||40.91|
|19||Carolina Panthers||31.35||19||Indianapolis Colts||40.41|
|20||Oakland Raiders||31.51||20||Miami Dolphins||40.23|
|21||Miami Dolphins||32.07||21||Carolina Panthers||40.00|
|22||Buffalo Bills||32.44||22||Dallas Cowboys||39.94|
|23||Tampa Bay Buccaneers||32.50||23||St. Louis Rams||39.26|
|24||Tennessee Titans||32.60||24||Jacksonville Jaguars||39.18|
|25||Kansas City Chiefs||32.97||25||Kansas City Chiefs||39.05|
|26||Atlanta Falcons||33.23||26||Washington Redskins||38.23|
|27||Jacksonville Jaguars||33.27||27||Oakland Raiders||37.62|
|28||Dallas Cowboys||33.85||28||Tennessee Titans||37.36|
|29||Washington Redskins||34.14||29||Buffalo Bills||37.35|
|30||Indianapolis Colts||34.61||30||Philadelphia Eagles||36.94|
|31||New York Giants||36.08||31||New York Giants||36.08|
|32||New Orleans Saints||37.66||32||New Orleans Saints||33.02|