On Sunday I noted that there was a 0.69 correlation between a rookie’s productivity and that player’s per-minute productivity the rest of his career. This was an exceedingly crude study. The only explanatory variable was rookie performance. Players who played more than 10 years were lumped in with players who played only two. In sum, this was not work that could be published in a real journal.
Fortunately, The Wages of Wins Journal is not a real journal. And despite the study’s obvious shortcomings, it does tell us something. NBA players, relative to baseball and football players, are really consistent.
Today I want to use the link between rookie and career performance to look back on the 2006 NBA draft. Twenty players drafted in 2006 went on to play at least 800 minutes in 2006-07. The performance of these twenty players this past season is reported in the following table.
The top rookie – in terms of WP48 (Wins Produced per 48 minutes) – was Renaldo Balkman. Balkman’s minutes were limited by his head coach (Isiah Thomas), so he only finished third in Wins Produced. Per-minute, though, he was the only rookie to post a WP48 that exceeded 0.200.
This led me to wonder, how often has a player posted a WP48 in excess of 0.200 and failed to be above average in his career?
Our sample of 308 players consists of all players drafted between 1991 and 2005 who played at least 800 minutes their rookie season. Of these 308 players, only 23 managed to post a WP48 in excess of 0.200 their rookie campaign. Of these 23 players, thirteen of these players managed to post a WP48 in excess of 0.200 after their first season. Another nine players managed to exceed the average mark of 0.100. And two players – David West and Antawn Jamison – have posted a WP48 after their first campaign that is below average.
Put it all together, and we see that 91% of all players who posted a 0.200 mark their rookie season went on to be above average. Again, it’s a crude study. Still, if Thomas ever chooses to play Balkman on a regular basis, he should get an above average level of production.
After Balkman we see seven rookies in 2006-07 who were above average. From 1991 to 2005 there were 64 rookies who posted a rookie WP48 that exceeded 0.100. Of these, 15 went on to post a mark in excess of 0.200. Another 33 managed to remain above average. So 48, or 75% of the above average rookies, remained above average. Of the 16 who were below average, 13 players managed to post a positive WP48 (yet below 0.100).
Okay, what if you weren’t above average your rookie season? This past year, seven rookies managed to have a WP48 that exceeded zero, but still below the 0.100 mark. Another five rookies were in the negative range, a group that included Adam Morrison, Andrea Bargnani, and Rudy Gay.
Since 1991 there have been 140 rookies who posted a WP48 between zero and 0.100. And another 81 were in the negative range. Of the 140 who were below average but positive, 53 – or 38% — went on to be above average performers. The negative performers, though, were not quite as likely to become good players. Only nine of the 81 negative performers, or 11%, went on to become above average players.
What does this mean for Morrison, Bargnani, and Gay? Our examination of the past 16 years suggests that it’s unlikely that any of these players will be good. And this is especially true for Morrison. His WP48 his rookie season was below -0.100. Since 1991 there have been thirteen rookies who were this bad (and none played as many minutes as Morrison). Of these thirteen, only three managed a WP48 after their rookie season that was above average. And none of these were close to 0.100. In sum, for Morrison to become a “good” NBA player would be truly exceptional.
Of course fans of these players – and probably their current employers – will insist that each player is the exception to the rule. And of course, that’s exactly what many of the employers of the below average rookies in the past probably thought. The data, unfortunately, tells us that more often than not, the exceptions are indeed exceptions. The general rule is that what we see from rookies is a good indicator of what we will see in the future.
Oh, by the way, I did consider a sample of rookies from 1992 to 2000 and I still found a correlation of 0.67. What I still need to do is consider other explanatory variables. People have suggested position played and the age of the player when he was drafted. Any other ideas? Comments are always welcomed.