# Nylon Calculus: Quantifying defensive versatility in the playoffs

If you have been following the NBA playoffs this season you’ve likely heard a lot about defenses switching screens. Switching is a defensive scheme where defenders switch the players they are guarding after a screen instead of trying to fight around the screener.

The tactic prevents openings that would have been caused by the screen, but can cause mismatches. With this, teams have emphasized acquiring long, versatile wings that can defend multiple positions.

An example of switching, and its disadvantages, can be seen below:

After passing the ball to Kevin Durant, Kevon Looney sets a screen on Clint Capela, forcing the switch and dragging Capela away from Durant. This leaves Durant isolated on the wing against the smaller Harden. For Durant, this is an easy drive.

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Thanks to NBA.com’s new matchup data, it is now possible to calculate how versatile a player is on defense. There are a few different ways to do this, but my preferred method is the HHI formula. I calculated the versatility rating for every player during the regular season (minimum 500 minutes played) and outlined the methodology here.

The first step is to match the offensive player with their corresponding position. To do so, I used Krishna Narsu’s (@Knarsu3) positional estimates, based on Basketball-Reference‘s play-by-play data. Krishna Narsu’s table is available here.

I then calculated the percentage of time a player spent guarding each position, and squared the percentage for each position. The sum of the squares for each player is their raw versatility rating. Following the summation, I took the square-root of the raw rating in order to reduce the distance between the most and least-versatile defender (taking the natural-log would work as well), and normalized the data so the maximum number is 1. The smaller the rating, the more versatile defender.

The top-20 most versatile defenders in the playoffs are listed below:

It is immediately apparent that defensive versatility is not a measure of defensive effectiveness. Although the list features some exceptional defenders — such as Luc Mbah a Moute, PJ Tucker, Trevor Ariza, Marcus Smart, Josh Richardson, Chris Paul and Draymond Green — it is topped by two below-average defenders. The versatility rating can be influenced by defensive schemes, and the offenses they are facing. It is not a coincidence both James Harden and Darius Miller faced the Warriors, and top the list. If a switching defense plays a sub-par defender, the opposing team will seek them out often.

The rating can be extended to teams by taking the average of the player’s ratings, weighted by possessions played. This step is done prior to the normalization. The team rating is normalized after.

Although the defensive versatility rating is not a measure of effectiveness, there does seem to be some correlation with success. Of the bottom-eight teams by the metric, none made it out of the first-round. Of the teams that made the Conference Finals, only Cleveland ranks outside of the top-four. In the regular season the top-four teams in terms of defensive versatility were Houston, Cleveland, Golden State and Boston, respectively.

The percentage change in the defensive versatility rating for each playoff team can be seen below:

Despite leading the NBA in defensive versatility during the regular season, Houston still managed to improve their rating the most in the playoffs. Even more shocking, Milwaukee saw the largest increase to their rating, despite already ranking as a below average team in terms of versatility during the regular season. Milwaukee’s roster looks primed to switch across most or all positions, but neither Jason Kidd nor Joe Prunty were able to tap into that talent.

The Western Conference Finals were a showcase of switching defenses, and versatile defenders. Golden State’s defense against Houston rates as the most versatile round played by any team, and Houston’s defense against the Warriors ranks as the second.

Despite LeBron hunting mismatches, defenses don’t seem to be particularly prone to switching against the Cavaliers. Their series’ against Cleveland rank as the least versatile for both Toronto and Boston. Indiana’s single series against Cleveland ranks as the least versatile defense any team played in the playoffs. Lack of off-ball screening and movement, relative to other playoff teams, may explain this effect as little cross-matching will happen.

The Warriors, Cleveland’s opponent in the NBA Finals, pushed the limits against both Houston and New Orleans. Against the Warriors, both teams posted markedly improved versatility ratings.

Next: What did we learn from the Warriors?

Take a deep breath, Cleveland fans, you will not like this next sentence: To have any kind of a chance against the Warriors, Cleveland will need Jeff Green to play well. Green ranks as the third most versatile defender in the playoffs thus far, ranked as the most versatile defender in the regular season and posted the most versatile series of any player against the Pacers in the first round. Navigating screens and switches is a necessity against the Warriors, and Green is, unfortunately, the Cavaliers’ most qualified defender outside of LeBron James.