Wednesday, March 11, 2009

ACC Conference Play: Devourer of Stats

A few weeks ago, I made a very critical post about the 2008-2009 Duke team. Having come off of a very poor stretch, the once promising Blue Devils seemed to be succumbing to conference play, with disastrous consequences. I concluded that Duke's pounding of non-conference foes was clouding our view of their standing, statistically speaking. Pomeroy's rankings simply cannot account for the evolution of a team throughout a season; they treat a November blowout win the same as a February blowout win. And conventional wisdom would treat the latter as more indicative of a team's chances in March.

With the ACC season complete I thought I'd take one final look at Duke's performance between conference and non-conference play. The result is not pretty:

In red are all the categories in which Duke is performing worse in ACC play compared to out of conference play (this includes 2009 games against Davidson, Georgetown, and St. John's). With the exception of turnovers on offense, Duke is not playing as well. But clearly, the level of play in the ACC must affect all teams. So I then tallied up every team's tempo-free performances. Rather than post another spreadsheet, the results can be found here. Some major points:

1) Nearly team saw both their offensive and defensive efficiencies drop when they were playing against ACC opponents. In fact, nearly every cell in the "Difference" part of my spreadsheet is colored red, meaning teams were also worse in other statistical categories. This probably makes sense, since the ACC is ranked the #1 conference by Pomeroy, and the #1 conference by Sagarin.

2) Overall, offense was less affected than defense. During ACC play, the conference teams averaged an efficiency of 104.5. Compared to the national average (100.1), it means that the ACC has an offense-heavy atmosphere. It would take further analysis to prove this point, but I believe this could have an effect similar to the "ballpark effect" in baseball; if the Oakland A's hit 300 home runs as a team, it would be more impressive than if the Colorado Rockies did it. By analogy I am suggesting that having a good offense in the ACC is not as impressive as having a good defense. This points a praising finger squarely at teams like FSU and Duke, the only teams to have defensive efficiency ratings below 100 during conference play.

3) Florida State is a major exception. While everyone elses' offensive efficiency was dropping, Florida State actually improved their offensive efficiency in conference play. A large part of this comes from another category-- turnover rate. Along with Duke, the Seminoles are one of two teams to improve their turnover rate on offense against ACC foes. Their effective field goal percentage and offensive rebounding rate were not as affected by conference play as well.

4) NC State is probably the biggest culprit of Cupcake Syndrome. The Wolfpack's offensive efficiency dropped by 8.4 points in ACC play (the worst drop the conference), and their defensive efficiency also dropped, by 18.0 points. They were an average team until January, and simply not a very good team in conference play.

5) There is no evidence for the conception "The ACC refs call more fouls than the rest of the nation." Collectively, the ACC teams went to the charity stripe during 35.4% of their possessions during league play, compared to 41.4% of possessions in non-conference play. While free throw rate is not a perfect proxy for the number of fouls called, it is obvious that the the ACC refs aren't as whistle happy as some would have you believe. On the other hand, during non-conference play, the opponents of ACC teams went to the free throw line in just 30.0% of possessions. There is certainly a connection between level of play and the number of fouls called; bad teams have bad defensive positioning and would tend to be whistled more often.

6) Continuing on the foul theme, Duke was near the top of free throw rate in conference (39.9%, 4th) and out of conference (46.2%, 3rd), but by no means any fuel for the DukeGetsAllTheCalls morons. In fact, every team (including Duke) saw their opponents go to the free throw line more frequently during ACC play, except one. That would be the Carolina Tar Heels, who inexplicably allowed free throws on 4% fewer possessions, compared to out of conference play. I'm not suggesting conspiracy, it's probably due to their Swiss cheese approach to half-court defense...

7) Wake Forest's defensive woes may be a bit misleading. Sure, they saw the biggest drop in defensive efficiency (19 points) of any team in the league. But, during league play they still have the best defensive effective field goal percentage, and the best defensive rebounding rate, of any team in the ACC. In this case, I'm guessing the problem was a cupcake pre-conference schedule (ranked 275th by Pomeroy), rather than some exposure by better competition.

8) Finally, we return to the most overanalyzed team in the country: Duke. It's amusing to me that any casual college basketball fan in the country right now can point to seven different reasons why the Blue Devils are not poised for greatness: they lack depth, they can't stop quick guards, they can't stop an inside presence, they don't play enough zone, they don't adapt in-game, ad nauseum. I wonder if those fans can note weaknesses so easily in other top 10 teams? Still, even I was receptive to this line of thinking a few weeks ago. But my comparison is clear: Duke is in the middle of the pack when it comes to their statistics being "affected" somehow by non-conference play.

In fact, contrary to my conclusions a few weeks ago, Duke's defense is one of the least affected by ACC play. On offense, Duke turns the ball over less frequently than any ACC team, and have respectable rebounding numbers for a team with "no inside presence." The lesson: stop making judgments in a vaccum; statistics can be misleading if they are not in a relative context.

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