Defense is all about keeping the other team from scoring. A player can be a good defender by getting a steal, a block, or a defensive rebound, but those stats offer only a snapshot of how effective a player is on defense. A player can also be an effective defender by denying the ball to an efficient scorer or by letting an inefficient scorer shoot more. Or by providing help defense in a way that does not expose other good scoring opportunities.
In order to make an attempt to better measure defense, I have developed a relatively uncomplicated statistic called "points saved." This differs from John Hollinger's points saved statistics because I measure it based on a per-possession number and quantify it over the course of the season. I do this because a guy who plays great defense for 80 possessions per game over the course of a season is more valuable than a guy who defends equally as well, but only plays for 20 possessions a game.
Points saved is calculated by comparing the defensive efficiency of a team when a player is in with the defensive efficiency of a team when the player is sitting on the bench. The number represents the amount of points a team saved (or lost, if the defender is poor) by playing a particular player instead of the other lineups that do not include the particular player. The second number is the amount of points saved per 100 possessions. This represents the amount of points saved by playing the player for an average NBA game instead of other lineups without the player.
There are a couple of major flaws with this system and for these reasons, this stat (like any other) should be taken as an incomplete measure of defensive prowess. First, if a player is on a bad defensive team, and he is a good defensive player, his numbers will be skewed to make him look like the greatest defender of all time (we'll call this the Raja Bell syndrome). Conversely, if the player is a good defender on a good defensive team, this stat will make him look worse than he actually is (Kevin Garnett syndrome). Also, this stat is heavily influenced by a player's backup -- if a player's backup is good, he is replacing the player with good defense which will skew the stat (Dwight Howard syndrome). So, it is important to keep in mind the context from which the stat is derived. Also, small sample sizes will mess things up. For instance, AI is on the floor virtually all the time and therefore there is a small sample size of Nuggets defenses without him.
Without further ado, here are the points saved totals for the 2007-2008 Denver Nuggets (only players playing 1000 possessions or more this season):
Eduardo Najera.................186.53
Allen Iverson..................144.82
Yakouba Diawara.................47.64
J.R. Smith......................38.87
Marcus Camby.....................7.68
Kenyon Martin..................-44.75
Linas Kleiza...................-58.89
Anthony Carter................-140.66
Carmelo Anthony...............-299.84
Points Saved/100 Possessions
Eduardo Najera..................5.42
Yakouba Diawara.................4.20
Allen Iverson...................2.04
J.R. Smith......................1.31
Marcus Camby....................0.13
Kenyon Martin..................-1.00
Linas Kleiza...................-1.51
Anthony Carter.................-3.42
Carmelo Anthony................-5.14
Here are the defensive efficiencies of the Nuggets when these players are in the game:
Yakouba Diawara................102.56
Eduardo Najera.................103.02
J.R. Smith.....................105.35
Allen Iverson..................105.91
Marcus Camby...................106.15
Kenyon Martin..................106.64
Linas Kleiza...................106.99
Carmelo Anthony................107.70
Anthony Carter.................107.91
Surprisingly, Eduardo Najera seems to be the best defensive player on the Nuggets. Also, there are none of the warning indicators that are discussed above: his backups are not particularly good or bad, he played about 40% of Nuggets possessions, and the Nuggets are neither a really good nor really bad defensive team. So there is a chance that he is a really good defender. This is probably because he is quick for a big guy and tries his tail off.
Anthony Carter is a bad defender. This may come as a surprise to George Karl, who played him all season because of his defense. Don't get me wrong, I LOVE Carter as a player (for his heart and determination), but he is not a very good professional basketball player. I don't know if I will be able to take it when I calculate his offensive numbers.
Carmelo is a VERY bad defender. This should surprise no one. The strange thing, is that I am not entirely sure he is that efficient on offense either. Maybe we should trade him before someone figures this out.
I believe that AI's numbers are skewed because the Nuggets rarely played without him. He is typically considered a poor defender. The numbers look a little more normal when calculated per 100 possessions, but I bet that this season was a fluke (at some point I will compare these numbers to previous seasons).
The 2007 Defensive Player of the Year is an average defender. This could be because he cannot guard big players by himself and because he only cares about blocks and rebounds instead of "defense." Or it could be because he has played the entire year with a fork sticking out of his back. At least he took the entire year off on offense in order to make the All-Defense 1st team again. That should look nice on his resume. Too bad it doesn't help his team. He is another trade candidate.
J.R. Smith is not bad considering he was benched for half the season because George Karl did not think he played any defense. Oh well.
Yakouba Diawara plays really good defense. This shouldn't surprise Nuggets fans. This could be the perimeter defender the Nuggets are looking for, however, I believe his offensive numbers may be poor. Surprisingly, the lineup the Nuggets used the second most often this season included Diawara (remember he played a lot early in the season) and it outscored their opponents by 60 points in only 169 minutes.
Please feel free to leave any comments or criticisms.
UPDATE: I am working on a formula to take into consideration the overall effectiveness of the team on which a player plays. This will make cross-team comparisons possible.
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