Nadal is the latest high profile player to pull out of the Grand Slam event.
Kyrgios has always been a critic of returning to competition amid the coronavirus pandemic.
Whether they play the US Open remains to be seen.
The tennis season has been at a standstill since mid-March due to the virus outbreak worldwide.
Last week world number three Dominic Thiem said that the tournament was "on shaky legs."
ATP chairman Andrea Gaudenzi said it was a lesson for other tournaments.
The Adria Tour has been cancelled as the fourth tennis player of the tournament tests positive.
Djokovic will also undergo a novel coronavirus test after other players were found positive.
Players will be undergoing daily temperature checks along with two COVID-19 tests every week during their stay in the USA
Despite winning his match against Zverev, Djokovic bowed out of the tournament
For the dress-up game, the young girls made their sportsman father wear a make-shift tiara and a Scotsman's kilt.
The 38-year old Swiss star is running out of opportunities and his fans are unsure whether he will appear in Wimbledon again.
The cancellation of the oldest Grand Slam tournament leaves the season in disarray, with no tennis set to be played until mid-July.
The newly rescheduled French Open clashes with the timings of several ATP and WTA tournaments
The Serbian star now has 17 Grand Slam titles under his belt.
Thiem is attempting to secure his first Grand Slam title.
After beating Zverev in the semi-final, Thiem became the first Austrian man to reach the Australian Open final
Rod Laver Arena's roof was closed to combat severe weather conditions
The Serb is aiming to win his 17th Grand Slam title after he stormed into the final, where he will face either Thiem or Zverev
Either Thiem or Zverev will face Federer or Djokovic in the Australian Open 2020 Final
While Federer won their last clash at the ATP Finals in November, the Serb has a psychological edge at the Slams.
The 16-time Grand Slam winner is aiming to lift his 8th Australian Open title