One of the facts that may have slipped quietly off the collective consciousness of Cowboys fans across the nation is that the Cowboys are one of only three teams in the NFL that have had a winning record over the last four years. Somewhat predictably, the Colts and the Patriots are the other two franchises.
From 2006 through 2009, the Cowboys have compiled a 42-22 regular season record, a marked improvement vs the 30-34 record of the previous four years. Coinciding with the Cowboys' improvement is the emergence of Tony Romo, the brief stint of the mercurial T.O. in a silver and blue uniform and Miles Austin literally bursting onto the scene last year. Consequently, a lot of the credit for the success of the last four years has gone to the offense.
But is the Cowboys' record really only a result of their offensive prowess, or was the defense an equally strong but perhaps more underappreciated driver of these results? One way to understand the contributions of each unit is to look at 'wins over average' for each unit, and that's what we'll do after the jump.
'Wins over average' is a metric developed by Doug Drinen at Pro-football-reference.com (PFR) in a post on adjusting QB records. I've taken his approach and modified it slightly to look at total offense and total defense.
Think back to the 7-6 win against the Redskins last November. Did the offense or the defense win that game for the Cowboys? Arguably, the defense did, because scoring 7 points (offense) is a pretty awful performance, while allowing only 6 points on two field goals (defense) is a pretty awesome performance. Instead of going with a totally subjective 'awful/awesome' rating, we approach this with a more objective, stat-based approach. This is how it works:
Assessing Awesomeness: As our measure of difficulty for the offense, we'll use points allowed, because it's a lot harder for an offense to win a game if their defense gives up 30 plus points than if they give up 10. For the defense, we'll look at points scored by their offense, as it's a lot harder to hold opposing defenses in check when your own offense is only scoring 10 points rather than 30 points.
In the table below I've crunched the number for all NFL teams for the last four years, so that's 64 games for each of the 32 teams for a total of 2,048 scores, and I've formed five clusters by points allowed/points scored and looked at the winning percentages for each.
Now, one team's points scored is the other team's points allowed, so the table below contains the same numbers for offense and defense, just reversed:
|Offense vs Points Allowed||Defense vs Points Scored|
How to read the table: An NFL offense almost always (352 vs 21) scores more points than the other team if the defense holds that team to less than ten points. The NFL average winning percentage is .944 in that situation. At the other end of the spectrum, when your offense scores 32 points or more, your defense is almost always (307-21) able to hold the opposing tem to fewer points for a winning percentage of .936.
Cowboys offense and wins over average: The Cowboys have a record of 17-1 over the last 4 years when the defense allowed 0-10 points. The average NFL team would be expected to also win 17 games (18 games x .944), so the Cowboys have 0 wins over average in this bracket. In the 11-17 bracket, the Cowboys have a 10-2 record, an average NFL team would be expected to win 8.5 games (12 games x .707), the Cowboys offense therefore gets 1.5 wins over average. Across all brackets, the wins over average total 7.0 for the offense as per the table below:
|Dallas Cowboys Offense|
|Wins over average
Cowboys defense: The Cowboys have a record of 1-6 over the last 4 years when the offense scored 0-10 points. The average NFL team would be expected to win 0.4 games (7 games x .056), so the Cowboys scored 0.6 wins over average in this bracket. Across all brackets, the wins over average total 3.3 for the defense as per the table below:
|Dallas Cowboys Defense|
|Wins over average
So statistically, the Cowboys offense generated more wins over average than the defense. The combined 10.3 wins over average ranks the Cowboys fifth in the NFL behind the Colts, Patriots, Chargers and Titans. Dallas' 10.3 wins over average are very close to their actual or 'real' wins over average: The average W/L for all NFL teams over four years is obviously 32-32, and with 42 wins over that period, the Cowboys 10 'real' wins over average are very close to the 10.3 the model delivers.
Wins over average (WOA) by NFL team, 2006-2009 (click column header to sort)
||Losses||Offense WOA||Defense WOA||Total||'Real' WOA||Difference|
As you click and read your way through the table above, some things pop out: The Colts & Patriots have dominated the last four years, and for that matter, the decade. The Saints have a much better offense than defense. The Ravens have a better defense than offense. The usual suspects in the Lions, Rams, Chiefs and Raiders have some of the weakest defenses. Was the Raiders offense really that bad? Yup, looks that way.
One thing that struck me was that the difference between Total WOA and the 'real' or actual WOA was quite big in some cases, especially for the Colts, Titans, Broncos and Panthers, all with a difference of more than 3.0.
After quite some digging around, I found a stat that had all four of these teams within the top 5: Record in close games. Over the last four years, these four teams all ranked within the top five in games decided by 7 points or less:
|Record in games decided by 7 points or less, 06-09|
Teams that rank at the bottom of the table in Difference between Total WOA and the 'real' or actual WOA all have a record below .500 in games decided by 7 points or less.
How your team performs in tight games, on offense or defense, ultimately decides who will win the game. And that is best illustrated by comparing the Colts and the Eagles:
|Records by score differential, 06-09|
|Tm||W/L record||Diff < 7points||Diff >8 points|
|Colts||51-13 (.796)||28-7 (.800)
The Eagles have a W/L record in games decided by eight or more points that is surprisingly similar to that of the Colts. It's in the tight games where you can best see the difference between the teams, and where the Colts are statistically twice as good as the eagles. It could be argued therefore that the difference between the Eagles and Colts is really only their ability to win close games. Of course, having Peyton Manning instead of Donovan McNabb can't hurt one bit. Regardless, the Colts record in close games is simply ridiculous.
The Cowboys are 13-10 in games decided by 7 points or less over the last four years and rank seventh in the league with a .565 winning percentage. It will take both the offense and the defense to make sure that the Cowboys win enough of the close games in the upcoming season to make the playoffs again.