Virginia’s Defense & Individual Defensive Points Per Possession | Stat Geek Idol

March 20, 2012 - by Kevin Myhre

***NOTE*** This is a winning Round of 64 entry in our inaugural Stat Geek Idol contest. This article was conceived of and written by Kevin Myhre of Wahoo Metrics. The opinions or predictions expressed below do not represent the views of TeamRankings.com, and are solely those of the author. This was written before Virginia’s loss to Florida. While we were unable to review, edit, and publish it before Virginia’s game, we felt it was still worth reading.

Defense:

A “non-negotiable” pillar of Tony Bennett’s system and the primary reason the University of Virginia Cavaliers are in the NCAA Tournament for the first time in five years.

Most Tournament teams are well aware of which key players will carry the offensive load, dictating the length of their tournament run. But for the Cavaliers, defensive play (and the continued offensive excellence of Mike Scott) will more likely determine their success.

Consequently, this post will try to address some key questions facing the Cavaliers defense heading into the Tournament: Who is the best defensive player on the team? Does this match perception? How badly will the season-ending injuries to Malcolm Brogdon and Assane Sene hurt the defensive effort?

The IDPPP (Individual Defensive Points Per Possession) Metric

Defensive performance has proven the most difficult to quantify in any sport. Although steals, blocks, and defensive rebounds are readily identifiable, a steadfast commitment to holding Bennett’s signature Pack-Line defense that forces a difficult shot does not have a simple numerical value. This is especially true in the Pack-Line, as the scheme relies heavily on team defensive shape. So, an off-ball defender could have made the best defensive play of the possession.

I was intrigued by the concept of plus-minus as a means of calculating defensive performance. Plus-minus is a deceptively comprehensive statistic that simply measures the difference in points scored and points surrendered while a given player (“Player X”) is on the floor.

This statistic captures such difficult concepts as Player X’s effect on the team as a whole, but also includes extraneous information of individual teammate performances. Theoretically, in the long run, as Player X is on the floor with various combinations of teammates, the effect of teammate performances will diminish. While some randomness is necessarily inherent in plus-minus analysis, hopefully the sample size employed here will allow for meaningful results.

To modify plus-minus into a defensive metric, I thought: why not just delete the offensive portion? We could track the total points surrendered while Player X is on the floor (effectively, “minus”). Better yet, we could standardize this metric by dividing Player X’s number of points surrendered by his number of defensive possessions, giving Individual Defensive Points Per Possession (“IDPPP”).

Virginia Cavaliers IDPPP Vs. RPI Top 100 Teams

I couldn’t find a source that tracked these statistics, so I went through the game logs and counted possessions. I limited the analysis to games against the RPI top-100; both for my own health and in an attempt to avoid inflation against non-Tournament-level competition.

The following chart shows the IDPPPs for the regular Cavaliers players, omitting in-season transfers and walk-ons who only saw garbage time. The Team DPPP does include contributions from players not listed.

(click to enlarge)

Defensive MVP And Perception

Jontel Evans was honored as an ACC All-Defensive Team member. According to IDPPP, though, Assane Sene takes the title of best Pack-Line defender. The IDPPP results do not precisely match perception, but Evans still has a very strong rating.

Some of Sene’s lead may be attributed to the fact that he only competed against the lower end of the RPI top-100. Alternatively, Sene’s ability to change an opposing offense simply due to his presence on the floor might explain the discrepancy. With a significant shot blocker, opposing teams are forced to rely on lower percentage outside shots to produce points.

Tony Bennett even acknowledged the loss of Sene as a major blow to the team’s defense beyond sheer physical ability, stating multiple times that Sene was the strongest communicator and leader in a defense that depends entirely on team coordination. IDPPP may have captured that non-physical portion of defensive prowess that often eludes measurement and common observation. Either way, Sene’s lead over Evans seems significant enough to crown him as the Cavaliers’ best defender.

Injuries

Given the above analysis, the loss of Sene is undoubtedly a major blow to the Cavaliers’ defense. The Cavaliers went 1-4 against the top-100 RPI without Sene.

Interestingly, Malcolm Brogdon might be the more subtly significant defensive loss. According to IDPPP, Brogdon was the third best defender on the team; quite an achievement for a freshman who became a strong first option off the bench as the season progressed. The Cavaliers made a valiant stand against FSU (for a second time) without Brogdon. Nevertheless, his absence could prove the difference in advancing in the Tournament.

Losing the first and third best defenders on a team that requires a stonewall-like effort to advance could spell disaster for the Cavaliers. Regardless of what happens in the Tournament, the Cavaliers have made significant strides this season under Tony Bennett. We’ll find out on Friday if the remaining defenders can form a sufficiently stout Pack-Line to advance against Florida.