College Basketball AP Preseason Top 25: Percent of Returning Production

The preseason AP college basketball poll came out a few days ago, and if you’re not a hoops junkie — if you don’t know which players were graduating seniors, what teams bring back all their starters, or who fell victim to the injury bug — you might not have much of an idea why teams are ranked the way they are. Specifically, why are Memphis, Vanderbilt, and Baylor so high? Why did Kansas fall almost a dozen spots from last season?

The answer is pretty simple: the first three teams listed above bring back most of their key players, while other top squads from last year — Kansas, Arizona, Kentucky — lost a lot of talent. But what to we mean by “a lot” and “most”?

Measuring Returning Production

To quantify the amount lost by each team, we calculated the individual Offensive Efficiency, Usage Rate, % of Minutes Played, and Defensive Rating (using definitions from Basketball On Paper) for every player from last year, and used those values to create a single “percent of returning production” value.

Here’s a quick overview of what the above stats measure:

  • Offensive Efficiency is an estimate of points scored per possession used by a player. Average is about 101.
  • Usage Rate is the percent of team possessions used by a player.
  • % of Minutes Played is exactly what it sounds like — percent of possible minutes played by a player.
  • Defensive Rating is similar to Offensive Rating, in that it is an estimate of points allowed per possession by a player. However, it’s different because Offensive Rating only counts plays that a player is directly involved in, while Defensive Rating counts individual blocks and steals, but also gives a player partial credit/blame for every other defensive possession (because all 5 men can guard the ball on defense, but only 1 can shoot it on offense). The result is that Defensive Rating already incorporates defensive usage rate, whereas Offensive Rating needs Usage Rate to provide context.

Using those four stats, we came up with simple offensive and defensive “Value Over Replacement Player” measures, roughly analogous to Cracked Sidewalk’s Value Add statistic, but without the opponent adjustments. [Nerds: the formulas can be found at the bottom of this post.] We then just summed all the player values to get a team value. From there it was easy to find what percent of the team value was contributed by players that will be returning for the 2011-12 season.

Finally, to get a single value for each team, we combined the returning offense and returning defense percentages using a weighted average. We figure it’s more important for good offensive teams to return their key offensive players than their key defensive players, and vice versa.

So, finally, here is the result, along with the final TR Predictive Power Ratings from last season, as well as the preseason AP rank for each team:

TeamReturning OffenseReturning Defense OverallFinal 2011 TR RankAP Poll
North Carolina86%80%83%131
Kentucky54%53%53%62
Ohio St58%61%59%13
Connecticut50%62%55%84
Syracuse80%77%79%145
Duke46%64%55%36
Vanderbilt97%95%96%347
Florida58%56%57%158
Louisville67%70%69%169
Pittsburgh57%53%55%410
Memphis86%89%87%8111
Baylor78%79%79%8012
Kansas26%32%28%213
Xavier70%59%65%3914
Wisconsin52%50%52%1015
Arizona54%57%55%1916
UCLA57%59%58%4917
Michigan71%84%77%2618
Alabama74%57%63%5019
Texas A&M56%66%61%4320
Cincinnati74%71%73%1721
Marquette59%63%61%2422
Gonzaga75%69%72%4223
California86%80%84%6824
Missouri79%73%77%4025

7 Lessons From The Data

A few teams stand out in the above table, some for good reasons, and others for bad:

  • North Carolina makes sense as #1. Out of all the teams that return over 60% of their production (UNC brings back 83%), they had the best 2011 rating.
  • Kansas was absolutely decimated compared to every other ranked team. The Jayhawks return barely a quarter of their production from last year. Next closest is Wisconsin with nearly twice as high a returning rate.
  • Vanderbilt lost basically no important pieces. Of course, they weren’t an elite team last year, so they’ll still need a lot of improvement from their returners to justify their top ten rank.
  • Alabama may be in trouble. Their main strength last year was their defense, but they return only 57% of their defensive production, for less than the 74% of their offense. Chris Hines was the biggest loss. He was below average on offense, but accounted for 16% of the Tide’s defensive production. Meanwhile, on offense, only three players account for all of the positive returning value — Tony Mitchell, JaMychal Green, and Trevor Releford.
  • UCLA appears overrated. The Bruins don’t look good by this metric, as they lose half of an already-not-awesome team. Of course, they have a couple transfers suiting up, which weren’t included here.
  • Connecticut and Duke should be alright on defense, but have a lot of question marks on offense. Both return over 60% of their defensive production, but under half of their offensive production. Of course, you didn’t need fancy numbers to tell you Kemba Walker, Nolan Smith, and Kyrie Irving would be missed.
  • AP voters like experience. Memphis returns the second-most production (percentage-wise) from last season, California the third-most, and Baylor the fifth-most. But they’re returning a bunch of mediocrity, judging by last year’s TR rank.

More To Come

Of course, we didn’t calculate all these player stats (Offensive & Defensive Rating, etc) just for this post. We’re hoping to eventually add them to our site, along with a variety of other tempo-free player stats.

In the meantime, we’re using the team returning production values to create a set of preseason ratings, which will be used to drive our season projections. Those should up soon. Follow us on Twitter at @TeamRankingsCBB or subscribe via email (on the right side of this page) to be notified when they’re posted.

And now, that note for the nerds that we promised earlier…

How We Calculated the Value Over Replacement Measures

If you’re familiar with the concept of a replacement player, you’ll find these fairly simple. Basically, we took the difference between each players ratings and those of a bad player, then multiplied them by the amount of possessions and/or minutes used:

Offensive Value Over Replacement Player = (Offensive Efficiency – 86) * Usage Rate * % Minutes

Defensive Value Over Replacement Player = (116 – Defensive Efficiency) * % Minutes / 5

You might think the defensive equation looks a little weird. Remember, the equation for Defensive Rating already accounts for defensive usage rate. It is essentially a measure of the team defensive rating, with an adjustment for the good/bad play of the player. So we take that team value and divide by the 5 players on the court. It’s a bit of a fudge, but it ends up creating Defensive VORP values that have about half of the range of the Offensive ones. This seems reasonable, given that box score data can shed so much more light on offense than defense.

As always, feel free to leave comments, questions, or suggestions below…