Controversial Australian tennis star Nick Kyrgios is in hot water again after sledging Swiss opponent Stan Wawrinka during their second-round clash at the Montreal Masters.

In a comment picked up by a courtside microphone, Kyrgios, 20, linked the reigning Australian and French Open champion with teenaged Australian player, Thanasi Kokkinakis.

“Kokkinakis banged your girlfriend. Sorry to tell you that mate,” said Kyrgios midway through the second set.

Wawrinka divorced his wife Ilham earlier this year.

On the eve of the French Open he was furious when the official tournament website linked him romantically with 18-year-old Croatian player Donna Vekic.

Kyrgios went on to win the second-round match in Montreal 6-7 (8-10) 6-3 4-0 after the third-seeded Wawrinka retired due to a back injury in the deciding set.

When asked afterwards why he made the comment, Kyrgios replied: “He was getting a bit lippy with me.

“Kind of in the heat of the moment. I don’t know. I just said it.”

Kyrgios has already drawn the ire of Australian tennis officialdom several times this year.

But Tennis Australia was thrilled that Lleyton Hewitt had agreed to take on a mentoring role with Kyrgios, beginning this week.

Hewitt and Kyrgios were beaten in the first round of the doubles in Montreal.

Kyrgios will play American John Isner in the third round of the singles at the US Open lead-up event.