We keep talking about how this year's team has the worst defensive efficiency in the Pomeroy era, so I thought it might be worthwhile to break it down and analyze the pieces.
According to Pomeroy, there are four factors that go into defensive efficiency: defensive rebounding percentage (what percentage of available defensive rebounds do you get); free throw rate (how often do you send your opponent to the free throw line); turnover percentage (what percentage of your opponents possessions end up in a turnover; and effective field goal percentage (shooting percentage counting made three-point shots as 1.5 and made two-point shots as 1.0).
Here's how this year's team stands up to the past dozen Duke teams:
Code:
Year DReb% ft rate to% eFG%
2012 65.7 30.1 20.0 48.0
2011 64.9 29.6 21.0 44.5
2010 59.4 34.0 21.4 43.6
2009 62.6 31.0 23.5 47.8
2008 66.0 31.9 24.7 47.5
2007 63.5 29.5 22.1 46.0
2006 69.1 27.6 22.5 46.1
2005 62.7 32.0 21.8 42.2
2004 60.7 31.9 24.4 44.7
2003 63.0 37.6 24.4 47.5
2002 65.5 32.1 25.6 46.0
2001 62.9 28.3 24.9 45.7
Our free throw rate is actually the 5th best of the 12 years, and our defensive rebound pct is the 3rd best. But the other two factors are the worst figures we've managed in the past dozen years. Having said that, our turnover pct is not all that different from several of the years, including last season and the 2010 national champs. But I think our defensive eFG% is historically bad (48%). Only three years I charted were even close to as bad (2009, 2008, and 2003), and in all of those years we had much better turnover rates.
So I broke it down further, looking at our D against threes, twos, and total overall. The last column in the table below is what percentage of our opponents' shots were three-pointers.
Code:
Year 3 made 3 att 3 pct 2 made 2 att 2 pct totmade tot att tot pct % threes
2012 88 269 0.327 405 849 0.477 493 1118 0.441 0.317
2011 176 543 0.324 720 1667 0.432 896 2210 0.405 0.326
2010 158 559 0.283 725 1643 0.441 883 2202 0.401 0.340
2009 183 542 0.338 722 1544 0.468 905 2086 0.434 0.351
2008 167 507 0.329 713 1518 0.470 880 2025 0.435 0.334
2007 139 441 0.315 626 1371 0.457 765 1812 0.422 0.322
2006 143 471 0.304 809 1744 0.464 952 2215 0.430 0.270
2005 128 420 0.305 655 1586 0.413 783 2006 0.390 0.265
2004 176 543 0.324 702 1614 0.435 878 2157 0.407 0.336
2003 164 474 0.346 675 1415 0.477 839 1889 0.444 0.335
2002 168 555 0.303 724 1559 0.464 892 2114 0.422 0.356
2001 207 602 0.344 821 1869 0.439 1028 2471 0.416 0.322
2000 197 551 0.358 737 1688 0.437 934 2239 0.417 0.326
1999 191 635 0.301 781 1849 0.422 972 2484 0.391 0.343
1998 156 512 0.305 685 1532 0.447 841 2044 0.411 0.334
1997 149 438 0.340 640 1433 0.447 789 1871 0.422 0.306
Our three-point defense seems OK. Six of the past 16 Duke teams were worse and two others were practically identical, so we're middle of the pack for a Duke team in defending the three. So far, so good. Except opponents try fewer threes against us this year than all but three of the past 16 seasons (2006, 2005, and 1997), which suggests the key lies in two-point shots. Where this year's team is tied for worst among the past 16 years in stopping the two-pointer.
I assume this means we're giving up a lot more dunks and layups than usual. Which I suppose I should have been able to guess without all the charts. Combine that with the low turnover rate, and it spells bad D, like we saw in the 2nd half against Florida State today.
How can we fix it? I don't know. Perhaps we should pack it in more, clog up the middle and force people to take more threes with people running at them, sort of like we saw from UVa. Maybe we need to take more chances and force more turnovers. Or possibly we just need to get better at rotating and/or stopping the penetration of opposing PGs.
Frankly, I was hoping for more illumination from the numbers, but you can't force the data. Since I did the work, I'm posting the charts, and maybe someone else will have a better idea.