According to some sports historians, professional tennis players develop unique playing styles that result from a combination of the peculiarities of each player's physical attributes and the influence of coaches during their early adaptation to the game. But when the increase in strength and endurance of modern players is discounted, it becomes readily apparent that the playing styles of the current crop of professional tennis players are no different from the styles of players from previous generations. Clearly, there is a universally efficient tennis style to which all professional tennis players conform.
The argument above is most weakened by which of the following statements?