Competitive balance is an important factor of sporting events since unpredictability is a crucial part of the fascination of sports. In this context, this study is concerned with the degree of competitive balance of Men’s tennis at the four Grand Slam Tournaments (Australian Open, French Open, Wimbledon, US Open) in the time span of 1991 to 2011. The influence of the seeding system, playing surface and results of top seeded players is measured by means of 10,622 tennis matches. Basic concept of this work is the structure-conduct-performance model which was originally developed in economics. The results of the investigated Federer-era (2004-2011) underline the decrease of competitive balance through a higher winning percentage of the top seeded players by contrast to the comparable time span (pre-Federer-era from 1995 to 2002). However, further variables (number of sets and number of tiebreaks in the finals) indicate an increase of competitive balance in the Federer-era. There is shown a higher level of competitive balance on clay in comparison to grass and hard court taking the lower level of winning percentage of the top seeded players into consideration. Through the analysis of different quality levels of players according to the seeding system, this study offers new stimuli with regard to possible impacts on the organizational form of tennis competitions.