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A look at defense and efficiency

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The previous statistical attempts to pinpoint a (or the) cause of UNC's struggles this year looking at guard play and turnovers were telling in that they really didn't tell us much at all. Neither pointed to a single area where one could say, "That's it! That's what is really holding the Tar Heels back!" As a result, there have been several people who have noted that there needs to be a closer look at how this team has played on the defensive side of the ball. To start, let's just look at how this team's defensive efficiency (opponent's points per 100 possessions) compares to the previous six Tar Heel teams:

[table id=14 /]

Once again, it appears that there is not a huge difference between the performance of this year's team and the 6 preceding it. The defensive efficiency of this team is on par for a Roy Williams' coached team and is slightly above average nationally. However, the difference here is that coming into the season this team's defense was supposed to be a strength, not a question mark like the perimeter play was. Everything we heard coming into the season was that this was not only going to be a good defensive team, but it had a chance to be an elite defensive team, and to this point, it just hasn't been. Has it been bad defensively? No, not at all, in fact, it is essentially playing defense at a level that allowed the 2008 team to go to the Final 4 and last year's team to win a National Title. The problem is, those teams were elite offensively, and when one studies the margin between UNC teams' offensive and defensive efficiencies it becomes easier to spot a trend:

[table id=15 /]

Now I must admit, this is a very small sample size, but nonetheless, the delineation between an "average" UNC team (based solely on the standard set historically by the program; by any other standard this would be considered a "good" team) and the "elite" UNC teams. All four of UNC's 30-win teams scored at least 21 points per 100 possessions more than they gave up, and the Title team's were at least 23 points better. [Side note: How did the 2007 team lose 7 games???] This year's team is a little less than 13 points better than what they are yielding, which puts them right in between the 2004 and 2006 teams. If the defense had played up to the expectations to this point (yielding say, 90 points per 100 possessions) then we are looking at a team that would have an Efficiency Margin of at least 18 (without taking into account any improvement the that would occur on the offensive side as a result of more transition opportunities), which would move this team closer to the territory of the "elite." Just how elite? Well take a look at the data collected from the last 40 Final 4 teams (since 2000):

[table id=17 /]

  • Wisconsin (2000) was the only team that had an Off. Efficiency less than 100.
  • UNC (2000) and Marquette (2003) were the only teams with a Def. Efficiencies greater than 100.

As you can see, a team with an Efficiency Margin of 18 or better is Final 4 caliber, so you can see where some of the pre-season rankings came from, for if UNC's defense was going to be that good, it was not going to have to do anything too heroic on offense to be great.