MONTREAL -- French Open champion Stan Wawrinka urged tennis authorities on Thursday to take action against Nick Kyrgios for an "unacceptable" comment during a match at the Rogers Cup.
Wawrinka wrote on his Twitter account:
A courtside microphone picked up the 20-year-old Kyrgios saying that Australian player Thanasi Kokkinakis had slept with a player who is reportedly Wawrinka's girlfriend.
"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," the 30-year-old Wawrinka wrote on Twitter.
Wawrinka, ranked fifth in the world, announced in April that he had separated from his wife, with whom he has a daughter.
The Swiss player has since been linked with 19-year-old Donna Vekic of Croatia, who is ranked 127th.
Vekic played mixed doubles with Kokkinakis, also 19 and ranked No. 76, at the 2014 Australian Open as a wild-card entry.
Kyrgios beat Wawrinka on Wednesday when the Swiss retired with a lower-back injury while trailing 4-0 in the third set.
In a post-match interview on court, Kyrgios said Wawrinka had provoked him.
"He was getting a bit lippy at me so, I don't know, it's just in-the-moment sort of stuff," Kyrgios said. "I don't really know, I just said it."
Later, Kyrgios issued an apology to Wawrinka on Facebook.
"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,"Kyrgios wrote. "I take full responsibility for my actions and regret what happened."
The ATP rule book allows a fine of up to $10,000 for incidents of verbal abuse or unsportsmanlike conduct.
The rules note that a "singularly egregious, a single violation of this section shall also constitute the player Major Offense of Aggravated Behavior."
Wawrinka's coach, Magnus Norman, also criticized Kyrgios, who has been at the center of controversy in recent weeks.
"That was really really low Nick Kyrgios," Norman wrote on Twitter. "Hope for u that u have people around that will teach u a thing or 2 about life tonight. Very bad."
At Wimbledon last month, Kyrgios was booed by spectators in a fourth-round loss to Richard Gasquet of France. Kyrgios appeared to make little attempt to return Gasquet's serve during the third game of the second set after a dispute with the chair umpire.
That incident prompted Australian swimming great Dawn Fraser to question the character of Kyrgios and suggest he could leave the country and return to where his parents came from.
Kyrgios, who was born in Australia to a father born in Greece and mother born in Malaysia, replied on Twitter that Fraser was a "blatant racist." She later apologized.