Eras of dominance: identifying strong and weak periods in professional tennis

In sports journalism and among fans, there is an ongoing debate on identifying eras where the level of competition is extremely high. In tennis, a common question concerning the advent of the so-called ‘Big Three’—listed alphabetically, Novak Djokovic, Roger Federer, and Rafael Nadal—is: Did these players lead to an unprecedented high level of competition? We contribute to this debate by identifying, from a statistical point of view, strong players, periods, and eras in men’s tennis, where a strong era is defined as a time frame in which a subset of (strong) players consistently dominate all the others. Hence, this work extends the idea of the Greatest Player of All Time (GOAT), largely investigated in the literature, to a dynamic subset of players. Through cointegration analysis of over 30 years of professional tennis data, we identify five strong eras. Interestingly, the player with the largest participation during these strong eras is Roger Federer and the most recent strong era concluded in July 2019. Moreover, we examine the relationship between the match duration and strong players/periods/eras, finding that the occurrence of a match between strong and not-strong players decreases the match duration, on average. Furthermore, when strong players meet, the match duration generally increases.