French Open champion Stan Wawrinka has described comments by Nick Kyrgios during their Rogers Cup match in Canada as "unacceptable".
On-court microphones apparently picked up the Australian, 20, making a lewd suggestion regarding Wawrinka's girlfriend in the match, which ended with the Swiss withdrawing with injury.
"There is no need for this kind of behaviour," said Wawrinka, 30.
"I really hope the ATP will take major action against him this time."
Speaking on court after his second-round win in Montreal, Kyrgios claimed he had been provoked by the world number four.
Kyrgios said: "He was getting a bit lippy with me.