Individual Defensive Ratings; Draymond, Embiid and Giannis On Top

By Stephen Shea, (@SteveShea33)

February 6, 2017

Historically, it has been far more difficult to quantify defensive performance than offensive production.  However, with recent improvements in data gathering, most notably the NBA’s adoption of SportVU’s spatial-tracking system, there is hope that analytics can begin to tackle this problem.

In a previous post, we presented Perimeter Defense Ratings (PDR).  Here, we present a slightly revised PDR (updated through the February 5^th games).  We also introduce an Interior Defense Rating (IDR) and sum IDR and PDR for Total Defense Ratings (TDR).

Methodology

For our calculations, we used steals, blocks, deflections, loose-balls gathered, defensive rebounds, opponents’ FG% on shots within 6 feet, individual defensive ratings (as calculated by NBA.com), pace, minutes played, opponents’ FGA within 6 feet, and 3-point shots contested.

Pace and minutes played were used to convert stat totals to per possession rates.  Opponents’ FGA within 6 feet and 3-point shots contested are used to approximate how often a player is in a position to influence perimeter shots and interior shots.  Steals, blocks, deflections, loose-balls gathered, defensive rebounds, and opponents’ FG% on shots within 6 feet are converted to standard deviations from the mean where the means and standard deviations are calculated on pace-adjusted numbers for NBA players with at least 600 minutes played.

Defensive rating is adjusted first for how well the player rated according to other stats.  A player that rated well on the individual metrics would see a bigger boost from a good DRtg than one that did not rate well on the other individual defensive stats.

Interpretation

Players were assessed based on their performance this season in the tasks asked of them.  For example, DeMarcus Cousins’ perimeter rating is based on his performance guarding the perimeter this season.  That often meant time guarding opposing bigs on the perimeter with the occasional switch onto a smaller player after a screen.  Cousins performed reasonably well in those areas registering a decent PDR.  This does not mean that Cousins should be asked to guard Steph Curry for 36 minutes.  (If he were asked to guard the opposing PG every night, he would probably have a terrible PDR.)

TDR simply sums PDR and IDR, which gives each stat in the sum equal weight.  This gives a good sense of the positional versatility of the defender.  However, there are players whose responsibilities lie almost exclusively on the perimeter or almost exclusively on the interior.  This can lead to some confusion in interpreting TDR.

For example, Greg Monroe scored a 3.1 in TDR by getting a 1.1 in PDR and a 2.0 in IDR.  The 1.1 in PDR reflects that Monroe is one of the more mobile big men on the perimeter.  The IDR of 2.0 suggests he has the size to be functional defensively at center but is by no means elite as a rim protector.  By comparison, DeAndre Jordan scored a 6.2 in IDR and a -3.8 in PDR for a TDR of 2.5.  Although Monroe outscored Jordan in TDR, it does not mean Monroe is a better defensive center than Jordan. Since teams rely heavily on their center to protect the rim, IDR alone is a better judge of a center’s defensive ability.

Where’s LeBron?  LeBron rates as a slight positive in both interior and perimeter defense.  However, his TDR rating of 1.2 does not accurately reflect how great of a defender LeBron can be.  His TDR reflects his contributions through the first half of this season, and it would be foolish for LeBron to be taking charges and diving for loose balls every possession for 37 minutes a night in November.  He’s a different defender when the games matter.  We suspect his playoff TDR would be much better than his regular season TDR.

Ratings

The following sortable table displays the defensive ratings for all players that have played at least 750 minutes this season.  There are 244 players in total.