Nick Kyrgios, ranked just 40 but a major drawcard, last month blasted the ATP as "selfish" for pressing ahead with plans for the US Open, which is scheduled to start on August 31.
Best known for his flamboyant persona and spectacular on-court tantrums, Nick Kyrgios has shown a different side in recent weeks as he took Novak Djokovic and other top players to task for their "stupidity" and risky behaviour.
Novak Djokovic, who recently tested negative for coronavirus after testing positive during his Balkans charity event, on Wednesday said that he still was not sure if he would play the US Open.
Alexander Zverev was heavily criticised after viral footage emerged of him partying in a busy bar despite pledging to "follow self-isolating guidelines" after playing in Novak Djokovic's coronavirus-hit Adria Tour.
Goran Ivanisevic is part of Novak Djokovic's coaching team and was the director of the now-abandoned Adria Tour which led to several top players becoming infected with the coronavirus.
Dominic Thiem took part in the Belgrade leg of the exhibition event organised by Novak Djokovic where social distancing was minimal and matches were played in front of thousands of fans.
Nick Kyrgios, Dominic Thiem and Alexander Zverev have been signed up to take part in Berlin.
Novak Djokovic has been criticised for hosting the exhibition tournament that has led to a slew of players testing positive for coronavirus, including himself.
Viktor Troicki became the third tennis player from Novak Djokovic's Adria Tour tennis tournament to test positive for coronavirus.
Novak Djokovic came under extreme criticism after two players tested positive after playing an exhibition tennis tournament.
Croatian tennis player Borna Coric has tested positive for coronavirus a day after Grigor Dimitrovs positive test led to the cancellation of the Adria Tour final.
Grigor Dimitrov said Sunday he has tested positive for coronavirus, just a week after he played an exhibition tournament alongside world number one Novak Djokovic.
Novak Djokovic addressed 4,000 fans packed into the Novak Tennis Centre on the banks of the Danube in the first leg of his Balkans charity tennis tournament.
The US Open main draw is due to get underway in New York on August 31.
Rafael Nadal will be the favorite to claim his third Acapulco title when he faces unseeded Taylor Fritz in the final.
Top seed Novak Djokovic came through a dramatic first-set tie-break before prevailing 7-6 (7/5), 6-4 to move to the brink of a record-extending fifth Bercy title.
Rafael Nadal is bidding for a record-extending 36th Masters crown and will take on Denis Shapovalov in the last four.
Novak Djokovic holds an 8-1 winning head-to-head record against Grigor Dimitrov, who saw off unseeded Chilean Cristian Garin 6-2, 7-5 earlier in the day.