John Albert Kramer (August 1, 1921 – September 12, 2009) was an American tennis player of the 1940s and 1950s, and a pioneer promoter who helped drive the sport towards professionalism at the elite level. Kramer also ushered in the serve-and-volley era in tennis, a playing style with which he won three Grand Slam tournaments (the U.S. Championships in 1946 and 1947, Wimbledon in 1947).
https://en.wikipedia.org/wiki/Jack_Kramer