Lies and statistics

Points allowed an erratic indicator of who plays best D

By John Hollinger, SI.com

If you look at the stats one way, you might think that the Miami Heat are a defensive juggernaut, while clubs like the Kings and Pacers are pretty ordinary. In fact, the exact opposite is true.

Allow me to explain. The way the league ranks teams defensively is by points allowed per game. Detroit is first by a mile in this category, permitting opponents just 85.8 points per contest. Miami is second at 89.0 a game, while Indiana and Sacramento are stuck in the middle at 15th and 16th, respectively.

Top Scoring Defenses Selected teams' NBA ranking Team  Pts. vs.  Rank  Detroit  85.8  1  Miami  89.0  2  New Jersey  90.0  5  Washington  91.6  6  Seattle  92.7  11  Indiana  94.1  15  Sacramento  94.3  16

The problem with that ranking is that it doesn't account for how fast teams play. Walk-it-up teams like Detroit or Miami use up a lot more time with each possession. As a result, their games feature fewer possessions and, thus, fewer chances to score.

To adjust for this, there's a better way to look at how teams are faring defensively, which I've introduced in this column before. I call it Defensive Efficiency, and it estimates how many points a team scores for each 100 possessions.

(To compute a team's Defensive Efficiency, take its opponents' free-throw attempts and multiply by 0.44. Add opponents' field-goal attempts and turnovers, and subtract opponents' offensive rebounds. Take points allowed and divide by this number, and multiply the result by 100. If reading that formula made you lapse into a coma, that's OK; I already did all the math. Just keep reading.)

Bringing the D Top teams in Defensive Efficiency Team  Pts. vs.  Def. Eff.  New Jersey  90.0  95.1  Detroit  89.0  95.9  San Antonio  89.5  96.1  Sacramento  94.3  96.3  Denver  89.5  98.0  Indiana  94.1  98.3

Taking a look at the leaders in Defensive Efficiency reveals the impact a team's pace has on its defensive ranking. The Heat and Pistons, for instance, are the two slowest-paced teams in the league. Once their snail-like tendencies are adjusted for, the Heat are no more than an average defensive team. Similarly, the Pistons, while still a top defending team, are no longer head and shoulders above the rest.

Slothlike teams like Washington (sixth in points allowed but 15th in Defensive Efficiency), Seattle (11th to 19th) and Houston (seventh to 14th) all fall down the charts once their slow pace is accounted for.

Meanwhile, several run-and-gun outfits fly up the charts. New Jersey, not Detroit, has been the league's most efficient defense thus far this season, a fact masked by their greyhound fast-break attack. Similarly, Indiana jumps up to sixth.

Lies and Statistics Biggest changes between Def. Eff. rank and pts. allowed rank Team  Pts. Rank.  D.E. Rank  Sacramento  16  4  Miamio  2  12  Indiana  15  6  Washington  6  15  Seattle  11  19  Houston  7  14  New Jersey  5  1

And the biggest jump is by Sacramento, which is easily the fastest-paced team in the league. The Kings are just 16th in points allowed but rank fourth in Defensive Efficiency.

To look at this closer, consider the Wizards and Pacers. Those two traded places in the rankings once we went from points allowed to Defensive Efficiency, with Washington dropping to 15th while the Pacers jumped to sixth.

Washington gives up 2.8 fewer points per game than the Pacers -- but the average Wizards game has 3.4 fewer possessions by each team. Given that teams average slightly more than one point per possession this year, it's clear that the Wizards would allow about one point per game more than the Pacers if their opponents had the same number of chances -- and thus, that they are the inferior defense between the two.

For a more extreme example, Sacramento's opponents have nine possessions more per game than Miami's. Given that, it would be amazing if the Kings didn't give up several more points per game than the Heat. Using Defensive Efficiency instead of points allowed helps even out those lumps, providing a clearer view of which teams are really the best at stopping their opponents.

John Hollinger covers the NBA for SI.com and is the author of Pro Basketball Prospectus.

 

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