Over the past few weeks Jeremy and I have continued to (slowly) roll out the results of some analysis we’ve done on The Four Factors. The relationships between the Four Factors and efficiency have been fairly well studied and established, however this has usually been done by looking at aggregate, league-wide data across multiple seasons. This helps establish how these statistical categories work together and overlap at a macro level, but we wanted to drill down to the micro.
We grabbed the game logs for each team from last season and calculated offensive and defensive efficiency, as well as the Four Factors and pace for each team in each game. This lets us look at that way these statistics relate to each other on an individual team level, which can often be very different from the league-wide trends. For example, in our first analysis we found that the Memphis Grizzlies, one of the best offensive rebounding teams, actually had a negative correlation between Offensive Rebound Percentage (OREB%) and Offensive Rating (ORTG). Although hitting the offensive glass was a huge strength for the Grizzlies it was a way of covering up for their other offensive holes. The more they were hitting the glass, the more other things weren’t working, and their overall efficiency was suffering.
Today we’re looking at the relationship between Defensive Rebound Percentage (DREB%) and Defensive Rating (DRTG), exploring how the ability to finish defensive possessions affects overall defensive efficiency. The individual team graphs are below.
This next visualization combines all the individual team information into one graph. The height of each bar represents how strong the correlation was between DREB% and DRTG. The color of each bar represents the team’s DRTG. The width of each bar represents their DREB%.
Interestingly, most of the best defensive teams had a relatively weak, or even negative, correlation between their DREB% and DRTG. Of the top five teams in Defensive Effective Field Goal Percentage (DeFG%), (San Antonio, Chicago, Indiana and Memphis) were in the bottom ten in the league for the strength of this connection between defensive rebounding and overall efficiency. This is a strange clustering and runs counter to what I would expect to see. Each of those teams rely so heavily on forcing their opponents to take contested shots. Collecting the inevitable misses is the endgame of that defensive focus and it’s surprising to see that those things weren’t necessarily tied together strongly. One possible explanation is that net negative of giving up an offensive rebound is much smaller for those teams since they will, theoretically, be able to defend the continuation of that possession with much of the same rigor that forced the initial miss.
Of course this makes the Oklahoma City Thunder stand out as an significant outlier. They had the league’s fourth best defensive efficiency and the league’s second best DeFG% last season. But unlike the other defensive powerhouses their was a fairly strong relationship between their ability to control the defensive glass and their overall defensive performance. For whatever reason, other teams were able to punish them on the offensive glass much more than teams like the Pacers, Grizzlies or Spurs. The Nuggets are also an interesting case where system may play a factor. With an offensive attack so predicated on getting out in transition it’s possible that players leaking out made Denver not just more susceptible to offensive rebounds, but made those ensuing possessions more likely to be successful for their opponents.
There are also some places where you can almost see the impact of single players. The Sacramento Kings had one of the worst defenses in the league last season and one of the strongest relationships between DREB% and DRTG. In that dichotomy you trace the outline of DeMarcus Cousins’ outsized impact. When he was engaged and able to play close to the rim the Kings defense was much improved. When he was pulled away from the basket and forced to defend in the pick-and-roll things began to unravel quickly.
If you see something I’ve missed, a trend or a pattern, anything that catches your eye, let us know! We have several more posts coming in this series, so stay tuned!