This blog has been one-dimensional this season: it can shoot the three, it can dish the rock, but it plays no defense. Today, I look at a defensive statistic that gets little press – the ability to prevent assists. See the stats page for the defensive assist percentage of all 330 teams.

Defensive assist percentage = assists allowed/total possessions

On Wednesday, the North Carolina Tar Heels were bottled up for 40 minutes like no other time this ACC season. They didn’t get many points on the fast break, and they didn’t get easy points out of the half-court set. UNC, a team that averages two assists on every three field goals made, had only ten assists in 25 made buckets. Shocking.

Or was it? In fact, there must be some skill at preventing fast breaks, preventing the smooth flow of the offense in the half-court, and thus preventing assists. It just so happens that the Duke Blue Devils are the best team in the nation at preventing assists. We can’t rule out that the Cameron scorer’s table is unusually stingy in awarding assists, given that Duke’s own assist total is exceptionally low. But since Duke doesn’t play all its games at home, the data has to be in the neighborhood of reality.

As a footnote, defensive assist percentage correlates less to an efficient defense than offensive assist percentage does to an efficient offense. You can look for yourself – while Duke and Kansas have great defenses and prevent assists well, there are some really bad defenses in the top 20 of defensive assist percentage.