# Defensive Win Shares

## What are Defensive Win Shares in Basketball?

Defensive Win Shares (DWS) is a basketball player statistic that aims to attribute credit to players based on their ability to prevent opposing teams from scoring. This metric is part of a greater concept known as Win Shares, which was first developed by Bill James for baseball to determine how many victories a player contributed to their team each season. This idea was later adapted for use in basketball, offering valuable insight into a player’s defensive capabilities.

To calculate DWS, an estimation of the number of points allowed per 100 defensive possessions is used. This complex calculation takes into account several factors, including player, team, and league-wide statistics. Overall, the sum of player win shares on a given team will be approximately equal to the team’s total wins for the season.

Understanding Defensive Win Shares helps basketball enthusiasts and analysts alike to grasp the impact a player’s defensive performance has on the success of their team. By evaluating DWS, one can identify key contributors to team victories and better appreciate the importance of a strong defensive presence on the court.

Contents

## Basics of Defensive Win Shares

### Definition and Purpose

Defensive Win Shares (DWS) is a basketball statistic that estimates the number of wins a player contributes to their team through their defensive abilities. It aims to highlight the player’s impact on the team’s success by preventing the opposing team from scoring. This metric is particularly useful in evaluating a player’s defensive performance and effectiveness throughout a season.

### Calculation of DWS

To calculate Defensive Win Shares, several factors are considered, including the player’s team’s defensive rating and the player’s individual contributions. Here’s a brief overview of the calculation process:

1. Calculate the team’s defensive rating, which is the estimated number of points allowed per 100 defensive possessions.
2. Determine the player’s individual defensive rating by analyzing various defensive statistics such as blocks, steals, and defensive rebounds.
3. Estimate the player’s defensive possessions throughout the season.
4. Calculate the player’s marginal defense by subtracting the product of their defensive possessions and the league’s average points per possession from their individual defensive rating.
5. Divide the player’s marginal defense by a specific value (usually around 0.32) to estimate the player’s defensive win shares.

It’s important to note that DWS cannot be solely relied upon to determine a player’s overall defensive prowess, as it doesn’t account for certain aspects like defensive matchups or the impact of a player’s teammates. However, it serves as a useful reference in assessing a player’s contribution to their team’s defensive success.

## Impact and Usage of DWS

### Interpreting DWS Values

Defensive Win Shares (DWS) is a basketball statistic that estimates the number of wins a player contributes to their team through their defensive abilities. Calculated using player, team, and league-wide statistics, DWS is an essential tool in analyzing a player’s overall defensive impact on the court.

A higher DWS value indicates a player is more effective defensively, and therefore more valuable to his team in terms of wins generated. Comparing DWS values among players can help teams and coaches identify strengths and weaknesses in their defensive lineup.

### Limitations and Critiques

Despite its usefulness, DWS has its limitations and is sometimes criticized for not perfectly capturing a player’s true defensive impact. Some of the key limitations include:

1. Overemphasis on team performance: A player’s DWS is affected by how well their team performs defensively, which can lead to players looking better or worse than they actually are due to their team’s overall performance.

2. Underrating individual defensive skills: Some excellent perimeter defenders, who do not generate many steals, may be underrated by DWS. As a result, their contribution might be overshadowed by players with higher steal rates.

3. Lack of consideration for specific situations: DWS tends to focus more on overall defensive efficiency and does not account for specific game situations, such as clutch moments when a player’s defensive impact might be more critical.

Although DWS remains a valuable metric for assessing players’ defensive abilities, it is important to consider these limitations when using it as a tool for evaluating performance. Combining DWS with other advanced defensive metrics can provide a more comprehensive and well-rounded understanding of a player’s defensive impact.