Optimal tournament design: lessons from the men's handball Champions League

Abstract: Many sports tournaments are organised in a hybrid design consisting of a round-robin group stage followed by a knock-out phase. The traditional seeding regime aims to create balanced groups roughly at the same competition level but may result in several uneven matches when the quality of the teams varies greatly. Our paper is the first challenging this classical solution through the example of the men's EHF (European Handball Federation) Champions League, the most prestigious men's handball club competition in Europe, which has used unbalanced groups between the 2015/16 and 2019/20 seasons. Its particular design is compared to an alternative format with equally strong groups, as well as to the previous scheme of the EHF Champions League. We find that it is possible to increase the quality of all matches played together with raising the uncertainty of outcome, essentially without sacrificing fairness. Our results have useful implications for the governing bodies of major sports.