Evaluating the 2008 NBA Draft

Conventional wisdom is that it takes about 3 seasons for a draft to shake out, in terms of evaluating talent. The 2008 draftees have now had an opportunity to play 3 full seasons, so let's look at how they stack up. I'm simply going to use ezPM here, but maybe in a future post will re-visit with RAPM.

Before I post a table of the draft picks, I'll make one significant observation of the data (well, I guess I should let you decide whether it is a "significant" observation). I wanted to see whether there was a correlation between playing time (possessions) and draft slot. To do this, I regressed possessions (in 2010-11) on draft slot and the past season ezPM100 ratings (obviously, I didn't want to use WARP, since that is directly correlated with both possessions and ezPM100). The results are somewhat surprising to me (although I recall others — including Berri using WP as the player metric — getting similar results):

Call:
lm(formula = POSS ~ DRAFT + EZPM100)

Residuals:
    Min      1Q  Median      3Q     Max 
-3290.8  -786.3   125.8  1000.6  1894.2 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept)  4458.18     390.08  11.429 1.07e-13 ***
DRAFT         -64.86      14.32  -4.528 5.99e-05 ***
EZPM100       106.79      72.50   1.473    0.149    
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

Residual standard error: 1313 on 37 degrees of freedom
  (20 observations deleted due to missingness)
Multiple R-squared: 0.3886,	Adjusted R-squared: 0.3555 
F-statistic: 11.76 on 2 and 37 DF,  p-value: 0.0001115

It turns out that there is a strong correlation between playing time and draft slot, but essentially no correlation for ezPM100. You can see these relationships in the plots below:

2008 draft re-visited three seasons later.

You see in the first plot (upper left) that WARP generally declines with draft slot, but this is mostly a function of playing time, which, in turn, is highly correlated with draft position (lower right for possessions or upper right for games started). There is essentially no relation between ezPM100 and draft position, although it should be noted that most of the last 10 draft slots didn't play a single possession this season (you can see those data points lying along the x-axis in the plots for GS and POSS). If you're curious, that's Semih Erden at #60. Overall, 40 of the 60 draft picks played at least a single possession this season.

Here are the players sorted in descending order by WARP:

 2008 Draft Class in 2010-11

The story is familiar by now. While it's great to have a top 3 or top 5 lottery pick, that is certainly not a guarantee of future success. Likewise, a late first round pick can easily turn out to be a quality starter in the league.

So, who made out like bandits in the 2008 draft? Clearly, the winners were Chicago (Derrick Rose and Omer Asik), Oklahoma City (Russell Westbrook and Serge Ibaka), and Los Angeles Clippers (Eric Gordon and DeAndre Jordan). Milwaukee got very good value out of their second round pick in Luc Mbah a Moute (drafted #37). The biggest disappointments thus far appear to be O.J. Mayo (drafted #3 and still with Memphis) and Michael Beasley  who was drafted second and is no longer with the team that drafted him (Miami).