Nikola Pilic was banned from 1973 Wimbledon due to his alleged refusal to compete in Yugoslavia's Davis Cup tie against New Zealand. As a result, 81 out of the other 84 ATP players, decided to boycott 1973 Wimbledon in protest, saying that professional tennis players should be able to pick and choose when to play Davis Cup. Of course, 3 ATP players refused to boycott (Nastase, Taylor, Keldie), and were later fined by the ATP for their participation in the tournament.
As regards to 1972 Wimbledon, all the WCT players were banned from ILTF Grand Prix tournaments from January until July that year, which included the French Open and Wimbledon. Andres Gimeno, the 1972 French Open champion, who had previously been a contract pro, had gone freelance at the end of the previous year.