Nick Kyrgios, who has been placed on probation by the governing body of men's tennis over his behaviour, hit out at Norwegian player Casper Ruud on Twitter on Thursday.
The Australian was responding to comments made by Ruud in an interview with Swedish tennis website Tennisportalen about their match at Rome in May where Kyrgios was disqualified after hurling a chair on to the court.
Ruud, who did not take kindly to Kyrgios's tweet then about how he had celebrated the victory, said the hot-headed 24-year-old was "completely crazy" and had behaved like an "idiot" on the court.
"Hey @CasperRuud98 next time you have something to say, I would appreciate you say it to my face, I'm sure you wouldn't run your mouth so much after that," Kyrgios, one of the most combustible characters in tennis, tweeted.
"Until then I will continue to rather watch paint dry than watch you play tennis, boring af.
"But again, I also understand why you have to keep my name in your mouth, because people don't even realise that you play tennis... good luck in Milan champ."
Kyrgios was fined $113,000 by the ATP over his meltdown at Cincinnati in August and courted more trouble at the US Open when he described them as "pretty corrupt".
He was given a suspended ban of 16 weeks and fine of $25,000 last month after an investigation found a pattern of behaviour related to Kyrgios's verbal abuse of officials and/or fans in the past year.
Both the fine and suspension are deferred pending Kyrgios's compliance with a set of conditions which will apply at ATP and Challenger Tour events during a six-month probationary period.
World number 30 Kyrgios, a devastating player when motivated and injury-free, was named in Australia's squad for next month's revamped Davis Cup finals in Spain.