Managing Randomness: How to Rethink Performance Evaluation and Decision-Making in European Club Football

Abstract

Football is a low-scoring sport in which a few single moments can change the result of an entire match, regardless of what else happened during the 90 minutes on the field. Thus, random forces can have a substantial influence on match outcomes. However, decision makers in European football clubs often rely heavily on recent match outcomes when evaluating team performance, which can lead to systematic misjudgments. In this paper, we propose a complementary approach for performance evaluation aimed at enabling decision makers to substantially mitigate the tendency to overlook the influence of randomness in match outcomes. We build upon the concept of expected goals based on quantified scoring chances and develop a chart that visualizes situations in which a team's true performance throughout a sequence of matches likely deviates from the performance indicated by match outcomes. The insights provided by the chart can systematically alert decision makers of professional football clubs about sensitive situations and should prevent clubs from making flawed decisions when match outcomes are overly biased due to the influence of random forces.