Defensive rating or defensive efficiency is a statistic used in basketball to measure an individual player's efficiency at preventing the other team from scoring points. It was created by author and statistician Dean Oliver.
The formula is: Defensive Rating = (Opponent's Points Allowed/ Opponent's Possessions) x 100. The result is the expected amount of points that an individual player will allow on defense over 100 possessions. This stat can be significantly influenced by the defense of a player's teammates.