The table below measures a player’s career impact on the defensive end. The columns labeled “Opp” show much a player affected the person he guarded (compared with his opponent’s average performance). The “box score” defensive stats – like blocks, steals, defensive rebounds, and personal fouls – measure a player’s defensive performance against per-possession league averages in the seasons he played.
In all columns, the impact is calculated as Actual – Expected. This means that for some columns (like Opp PTS or Opp FGM), it’s better to have a negative score. A negative score means that opponents guarded by this player tended to do worse against him than they did in other games. There are some columns, however, where it is better to have a positive value. Having a high number for Opp TOV means that a defender caused his opponent to turn the ball ball over far more often than the offensive player normally would.