NBA chemistry: Positive and negative synergies in basketball

We introduce a novel Skills Plus Minus ("SPM") framework to measure on-court chemistry in professional basketball. First, we evaluate each player's offense and defense in the SPM framework for three basic skill categories: scoring, rebounding, and ball-handling. Next, we simulate games using the skill ratings of the ten players on the court. Finally, we calculate the synergies of each NBA team by comparing their 5-player lineup's effectiveness to the "sum-of-the-parts." We find that these synergies can be large and meaningful. Because skills have different synergies with other skills, our framework predicts that a player's value depends on the other nine players on the court. Therefore, the desirability of a free agent depends on the current roster. Indeed, our framework generates mutually beneficial trades between teams. Other ratings systems cannot generate ex-ante mutually beneficial trades since one player is always rated above another. We find more than two hundred mutually beneficial trades between NBA teams, situations where the skills of the traded players fit better on their trading partner's team. We also find that differences in synergies between teams explain as much as six wins and that teams are no more likely to exhibit positive chemistry than negative chemistry.