ILTF & WCT rivalry and creation of the Association of Tennis Professionals (ATP)

The first WCT tournaments were held in February 1968 and the first NTL tournaments in March 1969. In spring 1970, the WCT absorbed the NTL.

In 1971, the WCT ran its circuit with 20 tournaments and the year-ending WCT Finals held in November. At the end of 1970, a panel of journalists ranked the best players in the world. This ranking served to the WCT organization to send invitations to the 32 best men to play the 1971 WCT circuit: among these 32 players, those who declined the invitation and stayed independent professionals (as opposed to the WCT contract pros) were Ilie Năstase, Stan Smith, Jan Kodeš, Željko Franulović and Clark Graebner. So in 1971, the majority of the best players in the world played mainly the WCT circuit and not the Grand Prix circuit, which principally consisted of the independent professionals.

The Australian Open was a WCT competition whereas Roland Garros, Wimbledon and Forest Hills were Grand Prix events. The conflict between the ILTF running the Grand Prix and the WCT was so strong that Rosewall, Gimeno, Laver, Emerson and other WCT players didn't enter the U.S. Open. There was a third professional circuit that year with the U.S Indoor Circuit run by Bill Riordan, future manager of Jimmy Connors.

In 1972, the struggle between ILTF and WCT ended with ILTF's ban of the contract pro players from January to July and consequently the WCT contract pros were strictly to play the Grand Prix circuit including Roland Garros and Wimbledon. At the U.S. Open where all players were together they set up a syndicate of players in order to protect them against the ILTF and national officials or the WCT promoters as well. Thus was born the Association of Tennis Professionals (ATP) in September 1972.

In 1973, there were four rival pro circuits: the WCT circuit, the Grand Prix circuit, the U.S. indoor circuit with Connors and Ilie Nastase and the European Spring Circuit with Nastase as their star.