Veteran French player Gilles Simon, a former world number six, said Friday he was taking a break from the rigours of the coronavirus-hit tour to "preserve myself mentally".
"My heart is no longer there to travel and play in these conditions. Unfortunately, I have to take a break in order to preserve myself mentally," the 36-year-old tweeted.
"Hoping that morale returns as soon as possible. Thank you to all the fans for your support. See you soon."
The ATP circuit was halted for five months last year due to Covid-19 and only returned under a series of tough health protocols.
In the run-up to the Australian Open, players were required to quarantine for two weeks and allowed out of their hotel rooms only to practice.
Simon was eliminated in the first round in Melbourne, losing in straight sets to eventual semi-finalist Stefanos Tsitsipas who allowed him just four games.
Simon, who has 14 career titles, is currently languishing at 68 in the world rankings.