Nick Kyrgios called Novak Djokovic a "tool" on Twitter for complaining about the COVID-19 measures in Melbourne ahead of the 2021 Australian Open.
The outspoken Australian fired a salvo at Djokovic after watching a local television report detailing the world No. 1's list of demands.
Players arriving from abroad for the Grand Slam tournament that begins Feb. 8 must observe a 14-day quarantine. But Djokovic asked organizers to move some players to houses with private courts, according to a 7News report. He also reportedly pushed to reduce the number of days in isolation and receive better food.
Players are staying in the five-star Grand Hyatt and Pullman and the four-star View Melbourne.
Breaching rules could result in hefty fines or a move to a more secure location with an active police presence.
Kyrgios also criticized Vanessa Sierra, the reality TV star and girlfriend of player Bernard Tomic who's in isolation. Sierra complained that Tomic couldn't train and that she has to wash her own hair.
"This is the worst part of quarantine," she said on YouTube. "I don't want to wash my own hair. I've never washed my own hair. It's just not something that I do."
So far, three people have tested positive after taking flights from Los Angeles. Sylvain Bruneau, who coaches 2019 US Open champion Bianca Andreescu, tested positive upon arriving from Abu Dhabi, and a member of a traveling party from Qatar also returned a positive result.
The 72 players who shared those flights are now under a hard lockdown and not permitted to leave their hotel rooms. The other players have been given permission to train outside under supervision for up to five hours per day.