Jefferson's defense in clear decline
As you know, this site expresses player performance according to their "Win Contribution" on each end of the court and the concomitant "Half Wins" produced as a result. Looking at the site basketball-reference.com, I notice they do a similar thing, with a bit of a twist.
B-R judges player performance according to points produced per possession while the player is on the court, with points scored refered to as the player's "Offensive Rating", and points allowed refered to as the player's "Defensive Rating" . B-R then converts those numbers into what they call "Offensive Win Shares" and "Defensive Win Shares". Each Win Share is worth a 1/3rd of a team win.
According to their system, my assessment of Richard Jefferson's offensive decline is inaccurate, but my assessment of his defensive decline is dead on. (Had we disagreed in precisely the opposite manner I would be worried. That's because my "Offensive Half Wins" system is based entirely on the work of Professor Berri, so I think I'm on solid ground with that. On the other hand, "Defensive Half Wins" are my own creation spun off from that work. Therefore I might have wavered had that been off, but it isn't.)
In fact, B-R says Jefferson had his best second best offensive performance last season, but that he also had by far his worst defensive performance. According to B-R, the Nets scored 112 points for every 100 possessions they had with Richard Jefferson was on the court, but allowed 112 points for every 100 possessions their opponents had with Jefferson was on the court. By those numbers, RJ's offensive performance was 2 points per 100 possessions better than his career average, but his defense was a whopping 8 points per 100 opponent possessions worse than his career average.
And their numbers say Jefferson's defense has been in free fall the last two seasons. In the 2005-06 season he had a defensive rating that matched his career average, 104 pts/100 possessions, then in 06-07 that dropped to 109 pts/100 possessions, and then this year of course it dropped even further to the 112 pts/100 possessions I cited above.
This might not be horrible news though, Antlerheads. In fact, I actually hope their numbers are more accurate than my own. That's because I think Skiles can probably coax a defensive renaissance out of Jefferson, but I'm not sure he can do the same for his offense.