Tennis bad boy Nick Kyrgios is once again in hot water after brutally trash-talking his Swiss opponent during a second-round clash at the Montreal Masters.
In a remark picked up by a courtside microphone, Kyrgios told third-seeded Stan Wawrinka a teenage Australian player, Thanasi Kokkinakis, slept with his girlfriend.
'Kokkinakis banged your girlfriend,' he said, midway through the second set. 'Sorry to tell you that, mate'.
Wawrinka, the reigning Australian and French Open champion, condemned the remarks in a fiery Twitter spree on Thursday evening.
'So disappointing to see a fellow athlete and colleague be so disrespectful in a way could never even imagine,' Wawrinka fumed. 'To [stoop] so low is not only unacceptable but also beyond belief'.
Kyrgios, 20, is believed to have been referring to Croatian tennis player Donna Vekic, 19.
Vekic has been romantically to Wawrinka, who divorced his wife, Ilham, earlier this year.
She was also one half of a mixed doubles team with Kokkinakis at the 2014 Australian Open.
Oblivious to the growing controversy outside the court, Kyrgios went on to trump Wawrinka 6-7 (8-10) 6-3 4-0 with the Swiss superstar retiring due to a back injury in the final set.
Asked afterwards why he made the staggering remark, he told a Canadian television station: 'He was getting a bit lippy with me.
'Kind of in the heat of the moment. I don't know. I just said it.'
It's just the latest controversy surrounding Kyrgios, whose on-court tantrums and misbehaviourhas drawn the ire of Australian tennis officials and fans alike.
At Wimbledon in June, he screamed out that an umpire was 'dirty scum'. A week later, he slammed his racquet into the ground with such force it bounced back up into the crowd.
During the competition's fourth round, he was forced to deny 'tanking' after accusations he did not even try to return serve.
But he no doubt had the support of most Australians afterwards when swimming great Dawn Fraser suggested he 'go back to where (his) parents came from'. She later apologised.
Tennis officials were said to be thrilled when another scrappy Australian tennis champion, former world no. 1 Lleyton Hewitt, took him under his wing this week.
Hewitt, famous for screaming 'come on!' on the court, agreed to take on a mentoring role with Kyrgios starting earlier this week.
Hewitt and Kyrgios are also playing doubles together in Montreal.