Bucks Diary

Friday, September 26, 2008

Is Al Jefferson the NBA's biggest defensive liability?

Using Professor David Berri's brilliant NBA "Win Score" efficiency metric, I developed a statistic that I believe is similar to baseball's "Value over Replacement Player". I call it "Win Contribution".

Basically, Win Contribution takes each player's Win Score above average and multiplies it by his percentage of overall playing time. Since any Win Score above the average would produce wins above the average (wins above the .500 mark), it follows that the average NBA player's "Win Contribution," for any given amount of playing time, would be +0.000, because his Win Score would be right at the average. And since a team of players with an average Win Score would produce an average record (please read Professor Berri's work for an explanation as to why), it follows that anything above +0.000 represents a player's contribution to a winning team (a team with a +0.500 winning percentage), and anything below represents a player's contribution to a losing team (a team with a -0.500 winning percentage).

Using the "Counterpart Opponents per 48 minute production" statistics on 82games.com, I took Professor Berri's work a step further. In my "Win Profiles" of each player on each team, I calculated not only the player's Win Score above average (and translated that into his "Wins Produced" using the professor's formula), I also calculated the Win Score above average of all the players that player guarded over the course of the season (and translated that into "Wins Produced" using the same formula). I then labeled the player's Win Score as his "Offensive Contribution" and his collective opponents Win Score as his "Defensive Contribution".

Okay. So, its important to remember that my definition of defense is very nontraditional. It has nothing to do with banging the floor or knocking the ball into row 76. All I care about is one thing: did the player allow the opponents he was assigned to guard to accumulate statistics that correlate with wins ? Thus, my definition of defense is "win prevention" rather than "scoring prevention". (That's why I think some scorers, who may not be viewed as technically sound defenders, like LeBron James and Dirk Nowitzki -- both of whom appear on my 20 Best Defensive Win Contributor list -- have a hidden defensive advantage. They force their "covers" to exhaust so much defensive energy, those opponents then become less than efficient all-around offensive players. That's an overlooked form of defense.).

One final point. Remember that "Win Contribution" is all about relative impact. Thus it is dependent on percentage of playing time. So, one player may make a more negative impact than another even though his Opponents' may not have a Win Score as far above average as another player's Opponents, simply because the first player is on the court a great deal longer.

Interesting Points about the List

1. Most people consider Marcus Camby an excellent defender. He routinely makes the all defensive team. But he's third on my "Worst Defensive Contribution" list. That's because when he's on the floor opposing centers grab more rebounds per 48 (+3.0), score more points (+1.6), commit fewer fouls (-1.4), and shoot a much higher percentage from the field (+4.1%). I think his lack of heft for a center, combined with his desire to roam and block shots sets his opponent centers free. And there's not much evidence that his shot blocking has any positive impact overall. The opponent shooting percentage is actually higher with him on the court. That said, he makes up for his defensive shortcomings with his production on the other end.

2. If I were to have extended this list and my "Best" list just a bit, the "Worst" would have included Sebastian Telfair's name, and the "Best" would have included Ray Allen's name. With that, every player the Celtics traded the previous summer, including draft pick Jeff Green, would have been on the "Worst" defenders list, while every player the Celtics picked up last summer, including draft pick Baby Davis, would have made the "Best" list. That's how you win a championship.

3. I doubt Bulls fans are shocked to see Ben Gordon's name at number 3. He's a horrible Win Producer overall. You just can't get very far with him as one of your main contributors.

4. Its somewhat understandable for player's who consume a great deal of playing time and who contribute a lot on the offensive end (ie Biedrens, Camby, Jefferson) to be on this list, but for bit players who suck on offense (ie Boone, Ivey, Rush, etc) to be on this list... that marks them out as serious liabilities.

5. I'll have my "Best" list out in a bit. Look for Paul Pierce's name front and center, and for some surprises down the list.


At December 24, 2010 at 7:09 PM, Anonymous Andy said...

Tha's stupid, because Royal Ivey is seriously on of the best defenders in the NBA. Might very well be the best defensive PG in the league! that is the only reason he survives in the league!!!


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