Complex sentence: A World No.1 player for a number of years, and one of the most important people in the establishment of modern men's "Open"-era tennis, he was considered the father and the leading promoter of the professional tennis tours.
Split into simpler sentences: A World No.1 player for a number of years, and one of the most important people to the establishment of modern men's "Open"-era tennis. He was considered the father and the leading promoter of the professional tennis tours.