Australian Nick Kyrgios has been fined and he's publicly apologised for an incendiary comment he directed at Swiss Stan Wawrinka during a match at the Rogers Cup tennis tournament on Thursday.
"I would like to take this opportunity to apologise for the comments I made during the match last night vs Stan," Kyrgios Tweeted.
He also posted the comment on Facebook, adding: "My comments were made in the heat of the moment and were unacceptable on many levels.
"In addition to the private apology I've made, I would like to make a public apology as well. I take full responsibility for my actions and regret what happened."
His apology came in the wake of news that Kyrgios has been fined the maximum on site amount of $US10,000 ($15,000) by The Association of Tennis Professionals, and he's since been fined another $US2,500 ($3,800) and could now face suspension too, over another comment made to a ball person during the match.
French Open champion Wawrinka branded Kyrgios "unacceptable" and called for action to be taken against him after the young Aussie appeared to make comments about his girlfriend during a second-round Rogers Cup match in Montreal.
Kyrgios won the contest after the Swiss retired hurt, but it was an apparent exchange at the end of the first set that became the focal point.
On-court microphones recorded Kyrgios walking to the net and saying: "Kokkinakis banged your girlfriend. Sorry to tell you that mate" - an apparent reference to the 20-year-old's Australian Davis Cup team-mate Thanasi Kokkinakis.
Wawrinka, who separated from his wife last year, has been linked with Croatian WTA Tour player Donna Vekic, as has Kokkinakis.
Speaking on court afterwards, Kyrgios claimed he had been provoked, saying: "He was getting a bit lippy with me. Kind of in the heat of the moment, I don't know. I just said it."
Writing on Twitter, Wawrinka said he was "So disappointing to see a fellow athlete and colleague be so disrespectful in a way I could never even imagine.
"What was said I wouldn't say to my worst enemy. To stoop so low is not only unacceptable but also beyond belief.
"There is no need for this kind of behaviour on or off the court and I hope the governing body of this sport does not stand for this and stands up for the integrity of this sport that we have worked so hard to build."
Controversy has followed Kyrgios around since his 2014 breakthrough when he knocked Rafael Nadal out of Wimbledon.
At this year's tournament he was moved to deny accusations of abusing an umpire and throwing a game, while on Davis Cup duty he shouted "I don't want to be here" while on court.