A method of processing data representing the performance of a tennis player in a display device includes: a) calculating, using data including physical quantities measured during a game period including one or several game sessions and transferred into a system for calculating of the display device, at least three parameters representing the player's performance during this game period, b) displaying, in the form of a diagram including one axis for each parameter, with the axes forming a star with several branches, points corresponding to the values of the parameters on the axes so as to form a generally polygon-shaped closed contour encompassing or passing through the points, and c) alternatively increasing and decreasing the surface area delimited by the closed contour according to a frequency of the variation calculated according to the effective game time of the player measured during the last game session of the game period.