How Do Player Substitutions Influence Men's UEFA Champions League Soccer Matches?

Abstract

Coaches' player substitution strategies can change the tactical behavior and the final result of matches. This empirical study aims to describe the relationship/association of player substitution variables with the results of men's UEFA Champions League matches during the 2018-2019 season. A total of 125 matches were analyzed using an ad hoc observation sheet created for this purpose. To measure the degree and strength of association between the variables studied, Chi-square and Cramer’s V tests were used, respectively. In turn, the Adjusted Standardized Residuals from the contingency tables were calculated to detect patterns of association. Likewise, a decision tree, in particular, the CHAID method, was used to predict and identify interactions. Player substitutions affect the final result and the findings prove it. An own team's goal after 5-10 minutes of player substitution was win-related (positive impact) (90.40%, ASRs = 10.40), while an opposing team’s goal after 5-10 minutes of player substitution was loss-related (negative impact) (90.30%, ASRs = 10.30). Regardless of the match status, the positive impact increased the winning percentage. Furthermore, the match status was postulated as an indicator of the need to make player substitutions. It showed that player substitutions could determine the final result when teams were tying. On the other hand, the match location was not a differentiating factor between winning and losing teams, although the winning percentage was somewhat higher for home teams. Coaches could use this information to establish player substitution strategies that would allow them to perform at their best.