Novak Djokovic was criticised for hosting the tennis tournament amid a pandemic after his coach Goran Ivanisevic and players Grigor Dimitrov, Borna Coric and Viktor Troicki returned positive tests over the two legs in Serbia and Croatia.
The 38-year-old Swiss national said he needed follow-up arthroscopic surgery after undergoing a similar procedure in February.
Roger Federer becomes the first player from his sport atop the annual list since its 1990 debut, rising from fifth in 2019.
All professional tennis tours were suspended in early March and will not return before August as countries went into lockdowns and closed borders to contain the spread of the novel coronavirus.
The former Australian, Wimbledon and US singles titleholder, was part of the golden era of Australian men's tennis in the 1950s, winning four major singles titles and four in doubles.
The current world number one, Novak Djokovic has 17 Grand Slam titles to his name - two behind Rafael Nadal and three fewer than Roger Federer.
Serbian tennis star Novak Djokovic caused a stir in a live Facebook chat with fellow Serb players on Sunday when he said that if a vaccination was compulsory when the tours resume, then he “wouldn’t want to be forced by someone” to take it.
Professional tennis came to a halt in March after countries started closing borders and imposed lockdown to contain the spread of the virus, and all events are currently suspended.
Patrick Mouratoglou said he was planning 10 closed-door matches to be broadcast live at his academy on each of five weekends under the title "Ultimate Tennis Showdown".
For the first time in decades the world is experiencing a shutdown in sporting entertainment with many clubs set to suffer financially
We look at how habits and techniques related to sports could change amid and after the coronavirus pandemic.
With London in its first week of lockdown over coronavirus outbreak, All England Lawn Tennis Club officials are weighing up their limited options.
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