Competing Against Former Teammates Predicts Team Victory

The small but growing body of research on team vs. team competition focuses on predicting the winner based on multilevel factors, including the team's strength and prior relations among team members within a team. Our research demonstrates the significance and power of prior relations among members between competing teams in predicting the outcome of a contest. Leveraging data over 8 seasons of the Indian Premier League (IPL), we demonstrate the effects of competing against former teammates on a team's victory in IPL matches. If two teams, A and B, are competing in a match, and n_A players from A are former teammates of players on B and n_B players from B are former teammates of players on A, then if team A has smaller values of n_A, it will have a competitive advantage over Team B with a higher value of n_B. We call the magnitude of the difference of n_A and n_B the "ecosystem" factor in predicting performance. Using regression and stochastic network models, we find that the ecosystem factor significantly impacts the outcome of a match. Our findings have implications for franchise owners. While recruiting a player, franchise owners should not rely solely on the player's ability but also leverage the rivalry between former teammates.