Earlier this month, the esteemed Luke Winn of Sports Illustrated wrote a piece placing Kentucky's defense into historical context. His conclusion: though the season isn't over yet, the Wildcats have a chance to turn in the best defensive season in the modern era. In fact, much has been written about UK's foray into the record books this year.
However, since that article was published, something's changed: Kentucky's defense is still historically good, but it is no longer the nation's best this season. Per Ken Pomeroy's adjusted efficiency stats, that honor now belongs to the Virginia Cavaliers, who allow .837 points per possession (adjusted for strength of opponent), compared to Kentucky's .847.
Even more impressive is that, over the past 14 seasons, the average efficiency has been about 1.014 points per possession, and it's up a tick at 1.018 this year. Thus, UVA (and Kentucky) are putting up outstanding defensive numbers during a year in which scoring is slightly above average.
How does that compare historically? For post-2002 data, KenPom.com has everything we need. And, using Luke Winn's calculations, we could compare Virginia, who is allowing .181 PPP under the national average, to elite defenses from before the "KenPom" era - he went back through 1987 to capture the beginning of the three-point/shot clock era. The 96-97 Kentucky Wildcats, who allowed .814 PPP have allowed the fewest points per possession of any team to date...but they did that in a defensive era, where the average team scored just .98 PPP.
Here's a look at the top defenses of the modern era, if the season ended today:
PPP below league avg.
Thus, with three regular season games to play (and hopefully 9 postseason games), the 2014-2015 Virginia Cavaliers are the best defensive team in the modern era. (And remember, these are efficiency numbers adjusted for strength of opponent, so UVA's adjusted numbers won't necessarily increase with the tougher competition to come.)
Looking at ACC play only, UVA continues to put up elite numbers. Moving to unadjusted terms here, UVA has allowed .866 PPP. That's also the best defensive efficiency in conference games in the "KenPom era." Second place in that category belongs to 2013-2014 Virginia (.910), and third belongs to 2011-2012 Virginia (.917).
It's true what they say about Tony Bennett - nobody does it better.