Do some teams consistently underperform against same opponents? - The curious case of the Croatian football league

This paper aims to determine if there are any matchups in 1.HNL that are characterized by the consistent over- or underperformance by one club against the other over the long run. If so, the study aims to test how significant these deviations are. To answer this question, we analyze over 5000 matches and all matchups that had ever taken place in 1.HNL, from seasons 1992 to 2015/16. We compare the realized number of points won by the teams in each matchup with the number of points each team was expected to win against the same opponent. To construct the expected number of points, we use the ClubElo formula that utilizes the Elo ranking system to measure the relative strength of teams. The results of our analysis indicate that one matchup extremely deviates from the expected distribution of points between the teams, and that matchup is Lokomotiva - Dinamo.