In recent years, football data has become widely available and evaluating teams is now possible, using scales. However evaluating the contribution of individuals in "team games" is particularly complex, both in sport and in other contexts, such as hospitals and universities, where individuals are the main determinant of results and people collaborate in clinical teams and groups of research.
Among sports, football is perhaps the most complex case, precisely due to the team structure, where players have specific roles, which require specific skills, but where role-changes are frequent during a match and the season. The complexity of the performance evaluation also depends on the numerous interactions between the individuals of the same team and the opposing players during a match. Therefore, the performances are strongly dependent on external factors that the individual cannot control.
In sports, as well as today in companies, performance measurement often takes the form of ratings (players receive points for performances like in football) or ranking (for example, players’ performance is ordered like the ATP in tennis). In particular, rankings are quite popular among fans, experts, analysts, bookmakers, but they can be also a useful tool for forecasts. Indeed, statistical analysis tools are common in professional sports to identify players with high sport-performances and low costs.