NBA Advanced Defensive Statistics

I've been working on some new defensive statistics which I need to introduce to the public.

Some of this builds on work developed by Dean Oliver. The rest I came up with on my own.

One of my biggest problems with statistics in general is that they are extremely biased in favor of offense. And advanced basketball statistics are no different.

I've been on a mission to create a statistic for everything a basketball player does to help his team win, or lose, and credit it accurately to improve player and team evaluation.

And these defensive statistics are another step in that direction.

I must again tell you that this article is about to get really nerdy right now, talking about the minute details of various basketball scenarios, so consider yourself warned.


INDIVIDUAL STATS

The first defensive concept is the stall.

A stall is mainly when an offensive player tries to score on a defensive player, but the defensive player prevents the scoring attempt, usually forcing the offensive player to pass the basketball.

It is a stall and not a stop because there was no shot attempt; the defender didn't prevent a score; he only delayed a scoring opportunity due to the possession being still alive with the ball in the hands of the offense.

Like almost everything else, some of these will be judgment calls; but you can usually tell when an offensive player is trying to score.

I'll stick with Oliver's language on this next one and go with forced miss.

A forced miss is when a defensive player forces an offensive player to miss a shot. He can do this by either contesting the shot or by blocking the path of the offensive player and forcing him shoot farther away from the basket than he could have without the path block.

Forced misses which are not contested and don't involve a path block will be credited to the team.

A forced miss plus a rebound equals a stop.

When the same player who forced the miss gets the rebound, he will be credited with a full stop.

A stop can also be defined more broadly as anything a defensive player or team does to create a change of possession without any points being scored by the offense.

So drawing charges, getting steals, forcing shot-clock violations and a wide variety of other things will be counted as stops as well.

And as Dean Oliver pointed out, fouling a player who goes to the line and misses both free throws will be counted as a stop, assuming the defense secures the rebound after the second free-throw miss.

½ Stops. When one player forces a miss and a different player gets the rebound, the stop will be divided into two equal halves, the forced miss half and the rebound half.

And each player will be given ½ stop.

¼ Stops. When two players force a miss or two players combine for a rebound, the ½ stop for the forced miss or rebound will be split in half and each player given ¼ stop.

Let's say two defensive players double-team a player in the post and force him to miss a shot, and a third defensive player gets the rebound.

The forced-miss half of the stop will be divided in two, and the two players will be given ¼ stop each for forcing the miss.

Since only one player got the rebound, he will be credited with his regular ½ stop.

¼ stops for the rebound half are for plays when one defensive player deflects the rebound, and a second recovers it.

Let's get really complicated and look at one more scenario.

A player dribbles the ball across half court and is immediately double-teamed.

The ball pressure from the trap forces him into a bad pass which is deflected by a third defender and recovered by a fourth for a steal.

This stop would be split into two equal halves, the ball-pressure half and the steal half.

The two trapping players would be given ¼ stop each for the ball-pressure half, and the players who got the steal would be given ¼ stop each for their combined play on the steal half.

Because these fractions can get out of hand, whenever more than two players combine for ½ of a stop, it will be credited to the team.


TEAM STATS

Now let's move over and look at some team defensive statistics.

The best way to stop a team from scoring is to not let them shoot the basketball.

You can't score without shooting, right?

So one of the things which will be tracked is the percentage of no-shot stops a defensive team gets, meaning they did something to change possession and get the ball back from the offense before the offense had the opportunity to attempt a field goal.

For a team which can't get a no-shot stop, a one-shot stop is the next best thing. That obviously means that the offense came down and missed one shot, and the defense got the rebound and ended the possession.

And the percentage of times a defense does that will be logged as well.

No-shot stops may be called "none-and-dones" and one-shot stops "one-and-dones."

Another thing is that not all stops are created equally.

Live-ball stops are the best because they give the team the opportunity to get fast-break points. So teams will be measured on their field goal percentages after live-ball stops, dead-ball stops and after made baskets for comparison.

These statistics can also be used for offense.

One of the biggest problems for Golden State is that they have too many no-shot possessions on offense. It absolutely killed them in road games at the Lakers and at Oklahoma City this year.

Finally, I'll be looking at dunks and layups.

I'm sure we can all agree that the two easiest shots to make in basketball are an uncontested dunk and an uncontested layup.

Field goals allowed will be looked at to see what percentage were uncontested dunks and layups and what impact this had on the field goal percentage allowed by the defense.

As I wrote before, I don't have nearly the resources or the manpower to track this information on a large scale but will do some games from time to time.

UPDATE: 1/31/2011

Here are some other situations where a player will be credited with a stall: (1) when he deflects a ball out of bounds, (2) when he deflects a ball which gets recovered by the offense, (3) when the offense is trying to pass to his man but his ball denial doesn't allow the pass attempt, (4) when his ball pressure on the passer forces the offense away from who it was trying to pass the ball to, (5) when he forces a jump ball and the offense maintains possession, (6*) when he bumps or blocks off an offensive player moving without the ball and disrupts the play, (7*) when he blocks the path of a dribbler not attempting to score and disrupts the play.

*UPDATE: 5/26/2011, 5:00 AM

It should also be noted that stalls can and will be divided into ½ stalls and ¼ stalls just like stops, and when more than two players combine for ½ of a stall it will be credited to the team.

Comment or e-mail: thenbaoutsider@yahoo.com
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