Momentum Effects in Team Sports: Analyzing the Interplay between Offense and Defense in the NBA

The phenomenon of momentum in sports has been explored in various studies; however, to date, there is limited evidence regarding the interplay between offense and defense. Using play-by-play data from the NBA spanning seasons 2015/16 to 2018/19, we investigate potential team-level momentum effects. Within a state-space modeling framework, we initially analyze offensive and defensive performances independently before integrating them into a joint framework. Our findings do not reveal evidence for momentum effects when the offense and the defense are considered in isolation. In contrast, we identify a (weak) momentum effect in the combined model. These results suggest that a successful defense performance affects the offense and vice versa. In addition, it underscores the necessity of including the interplay between offense and defense for an accurate analysis of momentum in team sports.