Who Won More Games For The 2010 Cowboys: Offense or Defense?

Think back to the opening day 7-13 loss against the Redskins last season. Obviously, what stands out from that game is the penalty called against Alex Barron that negated a winning TD pass to Roy Williams on the last play of the game.

But as I was mentally reviewing that game, I began to wonder whether that game hadn't been lost much earlier. If you look at the final score, one could argue that the offense lost that game, because scoring only 7 points is not a good offensive performance by any measure, while allowing only 13 points on one fumble return and two field goals is a pretty good defensive performance.

This in turn got me thinking about the entire season, and whether there was a way to quantify which unit, offense or defense, was more responsible for the Cowboys' 2010 record. One way to understand that 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. This is how it works:

'Wins over average' looks at an historic average to determine how likely it is that an offense will score more points relative to the points allowed by the defense. For example, if your defense allows only 10 points, you can reasonably expect your offense to win that game by scoring more points. If your defense were to allow 30 points though, it's a lot harder for an offense to win the game. And vice versa.

To determine the historic average, I've crunched the numbers for all NFL teams for the last five years in the table below, so that's 80 regular season games for each of the 32 teams for a total of 2,558 scores (minus one tied game). I've formed five clusters by points allowed/points scored and looked at the winning percentages for each.

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.

How to read the table: An NFL offense almost always (426-27) scores more points than the other team if the defense holds that team to ten points or less. The NFL average winning percentage is .940 in that situation. At the other end of the spectrum, when your defense allows 32 points or more, your offense is hardly ever (29-389) able to outscore the opposing team. And the same is true for the defense, only in reverse: when the offense scores 10 points or less, the defense almost always allows more points to the opponent (27-426) for a meager .060 winning percentage. The more points the offense scores, the more likely it obviously that the defense will hold the opponent to fewer points.

2010 Cowboys offense and wins over average: Now that we've established the average winning percentage in the NFL for each points bracket, we can look at how the 2010 Cowboys performed against that average. The Cowboys have a record of 2-1 in three games in which the defense allowed between 18 and 24 points (35-19 win against the Lions, 33-20 win against the Giants, 21-24 loss against the Vikings). The average NFL team would be expected to win 1.4 out of those three games in this points bracket (3 games x .478). By winning two of the three games, the Cowboys recorded 0.6 wins over average in this bracket. Doing the same exercise across all brackets in the table below, the 2010 Cowboys offense therefore gets 0.9 wins over average.

Small sample size warning: doing this exercise with only 16 games is a little bit shaky from a statistical point of view. But hey, it is what it is. If you don't like it, go to Goodell and ask for more regular season games.

2010 Cowboys defense: We use the same approach with the defense. The Cowboys offense scored between 25 and 31 points 5 times last season (26 against the Cardinals, 27 each against the Eagles, Saints, Texans and Titans). Scoring that amount of points should normally be enough to win, and in fact, the average NFL team would be expected to win 3.7 out of those 5 games (5 games x .749). But the Cowboys only won one of those five games, so the Cowboys defense gets -2.7 wins above average (or below average in this case) in this points bracket. Across all brackets, the wins over average total -4.1 for the defense as per the table below:

So statistically, the Cowboys offense generated more wins over average than the defense. If you take an 8-8 record as your average, the offense played roughly like a 9-6 team while the defense played roughly like a 4-12 team.

If you watched any of the games last year this should not come as any kind of a surprise, and you might wonder why we would to prove something with numbers that was so painfully obvious to the naked eye anyway. Heck, it's the offseason, we're in a lockout, what are we going to do? It's not like we have breaking news rolling in by the hour.