Monday, March 09, 2009

2009 ACC Tournament Predictions

Some of the hardest days as a sports fan come during early March; the worst of all are the four days between Selection Sunday and the first full day of NCAA tournament games. For this ACC fan, it is equally hard to bear the four days between the Duke-Carolina rematch and the start of the ACC tournament. Sure, there are plenty of actual games between now and then, but few of them actually matter, save the random upset of a top 25 mid-major and the corresponding bubble implications. To pass the time, I repeated an exercise I completed two years ago this week: predictions for the ACC tournament using the log5 method.

There will no doubt be predictions using Ken Pomeroy's rating system, all over the internet. (Here's one simple example.) I want to do something different; how do the predictions change, based on whether I use:

1) Winning Percentage
2) Raw Points Scored/Allowed
3) Pomeroy's Rankings (Full Season)
4) Raw Efficiency (ACC Games Only)

What follows are four Google spreadsheets tallying the information. Each sheet has three tabs: the calcuated winning percentage for each team. For tests 2 through 4, my formula follows Ken Pomeroy's: PF^11.5/(PF^11.5+PA^11.5). The next tab shows the chances that the team in a given column will beat the team listed in a row, using the "log5" formula, discussed here. Finally, mindful of the ACC Tournament Bracket, I predict each team's chances to advance to the Quarterfinals, Semifinals, Finals, and their chances of being 2009 ACC Champion. Let's start with raw winning percentage.

So you can see that Duke has an .806 winning percentage, a 31.6% chance of beating UNC, and a 15. 6% chance of winning the ACC tournament. Of course, winning percentage is kind of silly, because blowouts and squeakers count exactly the same. For this reason many baseball stat-heads turned to Pythagorean Win Percentage, which calculates a team's likely winning percentage given how much they score and how much they allow. This can be applied to basketball as well, with the following result:

Some pretty big changes already. First off, Duke has vaulted above Wake and is now favored to make the finals against a still-overwhelmingly-favored UNC team. The middle of the pack has changed considerably; Miami has doubled their chances, while Clemson has had theirs halved. We know that the Pythagorean Winning Percentage is flawed, Baseball Prospectus also follows what they call "Third Order Wins." By this they mean that how much offense/defense is not as important as the context in which the points were scored.To put it in 2009 terms, which team has the better offense:

VMI-- Points/Game: 93.8 Possessions/Game: 81.2
Duke- Points/Game: 78.7 Possessions/Game: 70.1

It is true that VMI scores 15 more points per contest than the Blue Devils; they are the most prolific scorers in the nation. However, VMI plays at the fastest tempo in the country, getting over 11 possessions more per game than Duke. Teams play different opponents every game, which could have a wide variance in the number of possessions. So, a fair comparison of offenses requires looking not at a team's raw scoring numbers, but at how efficiently a team scores in the possessions it gets. With this, it is clear that Duke has the better offense.

So what if we were to predict the results of the ACC tournament using Offensive and Defensive Efficiency, as provided by Ken Pomeroy? For this run I will also take each team's schedule into account by using Pomeroy's "Adjusted" efficiency ratings; teams are penalized if they run up high efficiencies against bottom feeding teams. The results are provided in an earlier link, but I'm showing my work:

While the chances of favorite UNC have remained largely the same, the effect of tempo-free statistics and the schedule have boosted Duke's chances by 5%. Most of this comes from an ever-increasing chance of beating Wake Forest on a neutral court: from 46% using just win percentage to 56% with Pythagoras to 62% tempo-free.

Frequently, when I use these tempo-free statistics, some folks are not convinced. They think that the adjustments for schedule made by Pomeroy are not enough, and that teams are different in league play than they were playing non-league foes before the new year. In addition, the ACC tournament is taking place between only ACC teams, so shouldn't statistics within the ACC matter more? On the other hand, the ACC no longer has a balanced schedule; for example, Boston College played Duke once (at home) while they played #12 seed Georgia Tech twice. I have not attempted to adjust for schedule here, so these are raw efficiency numbers:

The most striking result is that the top three teams (UNC, Duke, Wake) have had their chances all go down, relative to the full-season Pomeroy ratings. These extra chances have been split among a few teams. Clemson's title chances went up by 3 percentage points. Florida State, whose defense has improved tremendously since the clock ticked to 2009, have doubled their title chances (as have Boston College).

NCAA Tournament Implications:
1) The 8-9 game is not the closest of the first round. That distinction belongs to NCSU vs Maryland, according to all four metrics. That is not a good matchup for anyone who thinks that Maryland is still on the bubble.
2) Virginia Tech is pretty screwed. Like Maryland, they are a 7-9 ACC team, and the committee doesn't usually take kindly to a sub-.500 conference record. They are probably out of the tournament picture unless they make it deep, and the statistics say it's not probable at all.
3) The final 7-9 team, Miami, has to avoid a collapse against Virginia Tech, and then they face 2-to-1 odds against in the matchup with Wake Forest. Should they prevail, would the committee consider what then would be a 20-win ACC team?
4) Statistically, the top three seeds are very heavy favorites for the semifinals, with Duke and UNC more likely to be there than Wake. Should Duke win the two games as expected, would they still have to beat Wake Forest to get a #2 seed in the NCAAT? Certainly, the Deacons probably need to win the ACC tournament to get their own #2 seed.
5) Clemson and Florida State should both be solidly into the NCAA tourament, but they are playing for favorable seedings. By the ACC numbers and the overall Pomeroy ratings, Clemson is favored in a matchup with Florida State, and the Tigers are more likely to knock off UNC.
6) Spreadsheets are fun!

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