Measuring Player Impact: Box Score, On/Off and Minutes

No single stat captures a basketball player's value. Box scores miss most defence; plus-minus is noisy and depends on teammates. We combine both, and weight them by what actually predicts future results.

The inputs

• Per-100-possession box production: points, shot attempts, free throws, threes, offensive and defensive rebounds, assists, steals, blocks, turnovers and fouls.
• On-court margin: the team's scoring margin per 100 possessions while he plays.
• On/off margin: on-court margin minus the team's margin while he sits.

All are time-decayed and shrunk toward a replacement-level player until the sample is large enough.

The weights come from prediction

Rather than hand-picking weights, we let the game model learn them: the weights that best predict future game margins from each side's expected rotation. A player's impact is then the points per 48 minutes his rates add, versus a replacement-level player, under those weights.

How to read it

+6 or more is MVP-level; +2 to +4 is a quality starter; around 0 is a rotation player. Impact is a rate, so a +5 player in 20 minutes adds less to a game than a +3 player in 36. Browse the player table.

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