Using SportVU to find the most overrated defenders in the NBA

dj block

By: Patrick Harrel

In the quest for advanced statistics capable of accurately quantifying defense, NBA analysts have always faced an uphill battle. Unlike offense, which had easily quantifiable measures of success, readily available statistics came nowhere close to establishing how effective a defensive player was on the floor. If a player blocked a lot of shots, he was often lauded as a tremendous defender, but what if those blocks came at the cost of missed rotations and wide open layups on failed attempts? Until very recently, we couldn’t dream of answering a question like that comprehensively.

When the NBA announced this year that they would be making the SportVU data available to the public for the 2013-14 season, the news was met with raucous applause from all circles involved with basketball. Writers loved it, fans loved it, and statisticians, who had always only been able to make educated guesses about certain factors, adored it. At Princeton Sports Analytics, we are going to make the data more accessible to you in a bi-weekly column, with each entry dedicated to a specific aspect of what is going on in the NBA.

If you are unfamiliar with SportVU, it is a system that is now installed in all 29 NBA arenas that tracks the movement of all 10 players on the court, the 3 referees, and the ball, and automatically generates an incredible amount of data about the various outcomes on the floor. It tracks average speed of every player, how many touches any given player gets per game, and much more.

Today, we’re going to discuss the ability to better quantify defense. Specifically, we will look at who have been some of the surprisingly poor interior defensive players this season. SportVU measures how well players defend inside by charting every shot attempt that an offensive player takes when a defender is both within five feet of the basket and within five feet of the offensive player. It then measures what percentage of shots the defensive player allows to be made under these conditions.

We’re trying to find ways to use SportVU to challenge our assumptions about players, so in this analysis, we’re looking at players who have high block totals but still do not perform great on defense. In that vein, we are going to limit our analysis to players who have blocked one shot per game. Additionally, in order to eliminate small sample size conclusions, we eliminate all players who have not appeared in four or more games or haven’t seen at least five shot attempts at the rim per game.

With all that said, here are the ten worst defensive big men in the NBA with at least one block per game:

chart

There is the obvious small sample size caveat that comes with analyzing data just one week into the season, but there are some interesting players on this list that are typically regarded as top defenders. DeAndre Jordan has always blocked shots, and he’s grown in reputation as a complete defensive player over the past couple of years, even getting Defensive Player of the Year love from teammate Blake Griffin a year ago. However in this young season, he has allowed 55.6% of shots at the rim to be converted, a testament to the fact that he might not be as good of a team defender as believed. Despite being top ten among NBA players in blocks, he could still use improvements with his defensive discipline. Meanwhile, Derrick Favors also appears on this list despite getting accolades after moving into the Jazz’s starting lineup with the departures of Paul Millsap and Al Jefferson.

Add in Jonas Valanciunas, Bismack Biyombo and Serge Ibaka, and it becomes clear that this list is a veritable who’s who for the league’s young shot-blockers. In this whole list, that appears to be the only common thread. With the exception of Bosh and Gortat, who were never regarded as particularly strong defenders, the remaining eight players on the list are all 25 or younger.

As we continue to get more data, the conclusions we make will only be able to be made more strongly, but it’s clear that SportVU will completely change the way we think about and evaluate players in the NBA, especially on the defensive side of the ball. With the exception of the rare transcendent players (see: Anthony Davis, who leads the league in FG% allowed at the rim), it’s unfair to expect any young shot-blockers to be particularly effective early on in their career, and the data that we’ve compiled thus far only strengthens this belief. Check back here in the next few weeks as we look more closely at the SportVU data in different ways.

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