This is a review of the sports analytics coaching assistance research conducted by Avery McIntyre, Joel Brooks, John Guttag and Jenna Wiens.
The ball screen (also called a pick and roll) is an offensive tactic that is regularly used in the NBA. To defend against it requires that the defense stop the ball handler from making the shot and denying the screener the opportunity to score. Failing to do this often results in the offense scoring points.
A step has been taken towards building a tool designed to help analyze the way ball screens are defended and determine relationships between defensive strategies and possession outcomes. This system takes in SportVU position data and identifies ball screens, the defensive scheme used, and the offensive outcome in terms of points per possession. For each ball screen four players are identified: the ball handler, the ball handler defender, the screener, and the screener defender. Defensive strategies are separated into four categories: (1) Over – when the ball handler defender stays between the ball handler and screener, (2) Under – when the player defending the ball handler does not stay between him and the person screening, (3) Switch – when the player defending against the ball handler switches places with the player defending the screener, and (4) Trap – when both defenders double team the ball handler.
This tool was then used to review four seasons of data in which over 270 thousand screens were identified. Information was collected regarding the defensive strategy, how many points were scored and which players were involved. As a result it is possible to determine how effective each of the defense strategies are in actual game action.
It was noted that the distribution of the four defensive strategies remained fairly constant over the four seasons. The over defense was consistently used far more often than the other three and the trap defense was used the least. Not all teams followed the same pattern as some teams were able to use the trap defense a greater percentage of the time with good success.
Teams typically decide which defensive strategy to use based on the ball handler’s offensive skill and shooting ability. Analysts are able to look at how individual players score against the different defenses. This will aide teams in deciding what type of defense to use against individual players. If the ball handler is particularly adept at scoring against the over defense then another strategy should be employed. If a ball handler has difficulty scoring against the over defense then this should continue to be used in that situation. Defensive strategies can be individualized to optimize the defense’s ability to prevent the offense from scoring.
Analysts can look at how well defensive pairings are able to execute the different defensive strategies. Analyzing the data suggests that players are not equally effective at all strategies. This would aide teams in determining how to best match up their defensive pairs with their most effective form of defense. Looking at how players do when paired up with different players allow teams to determine how to optimize their players in different situations.
This tool can be used by teams to quickly and easily assess a player’s performance during a game and use that information as a guide for developing strategies to improve that player’s skills. Teams can also use this tool to identify areas of poor defensive performance and focus on improving these for future games.
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