Last season was Duke’s worst defensive team statistically since Ken Pomeroy began keeping records in 2003. Their adjusted defensive efficiency ranking of 70 was the first time they hadn’t finished in the Top 20. That was actually an improvement over where they were in late January, when I did an interview with Mike Miller of NBCSports.com and they were at a paltry 84.

This was clearly an area of focus for the team coming into this year, as Coach Mike Krzyzewski lamented in his preseason press conference.

“One of our goals is to be better defensively,” Krzyzewski said. “The history of our program has been based on sound, good team defense. I don’t think we had that [last year]. I think we beat teams offensively last year. When you don’t have the defense, I think you miss out on a certain toughness and togetherness that’s only really found by doing things on the defensive end of the court.”

So have they improved? Let’s look at a few metrics and try to get a gauge on their performance on the defensive side of the ball this season compared to last.

Points Per Possession

One of the better ways to measure how efficient a team or player has been playing is how many points they average per possession. The only way to get close to evaluating teams that play different paces is by looking at how efficient an offense is per 100 possessions.By looking at what Duke was able to hold these team to in points per possession and how they’ve done overall, we can get an idea as to how effective Duke’s defense has been in comparison to others.

As you can see by the chart above, Duke has held every opponent they played to below their season average on points per possession. Four opponents (Georgia State, Minnesota, Ohio State and Delaware) had their worst points per possession outings against the Blue Devils. So far, Duke’s defense has been excellent. Even against the tough schedule they’ve played so far.

Offensive Efficiency

While points per possession looks at teams’ production on a more micro level, offensive efficiency attempts to look at statistical output on a macro level. There is no crazy formula here, it’s just points per 100 possessions. When trying to compare teams that have a fast tempo against a team that plays a slower tempo, per game stats don’t tell the whole story. Let’s look at Duke’s first games to see how the Blue Devils did defensively.

Duke again held every opponent to below their season average in offensive efficiency. Georgia State, Minnesota, Ohio State and Delaware all turned in their worst offensive performances of the year against the Blue Devils.

Effective Field Goal Percentage

Last year, Duke allowed teams to shoot an effective field goal percentage of 47.1% on the year. Only one other year (2009) did they allow a higher number. A major contributing factor to this was a shaky, at best, perimeter defense which allowed opposing guards to penetrate and break them down off the dribble. This has improved greatly on the year so far, with the toughest schedule in the nation averaging only 42.4 eFG% against them.

If you’re noticing a common thread here, Duke held every opponent below their season average for effective field goal percentage, just like for offensive efficiency and points per possession. Minnesota, VCU, Ohio State and Delaware all shot the ball worse against the Blue Devils than they did in any of their other games.

Judging by these metrics, it’s easy to see that Duke’s defensive issues have been corrected thus far in the season. Seemingly, their performance should not decrease as the season progresses seeing as the toughest part of their schedule is behind them. NC State (11th), Davidson (25th), Miami (28th), Virginia Tech (38th), UNC (47th) all pose the biggest threats offensively to bringing down these numbers of the teams remaining on Duke’s schedule.