In the wake of Nick Kyrgios's highly personal comments during their Rogers Cup match, French Open champion Stan Wawrinka pulls no punches

MONTREAL – Nick Kyrgios said he "could feel some tension in the air" during his match against Switzerland's Stan Wawrinka Wednesday night at the Rogers Cup. There had been precedent between the two.

Well, the tension escalated significantly when Kyrgios made it personal early in the second set.

Wawrinka had words with Kyrgios, who had been serving at lightning-quick speed during that game, not waiting for the ball kids to clear the court after a missed first serve.

After Kyrgios held in the first game, he decided to fire back, declaring to Wawrinka (in rather indelicate terms), that Kyrgios's friend and countryman Thanasi Kokkinakis had, well, been intimate with Wawrinka's girlfriend.

Their relationship has not gone public, in the wake of Wawrinka's rather messy breakup with wife Ilham Vuilloud . But Wawrinka, 30, is said to be dating Donna Vekic, a 19-year-old Croatian player on the WTA Tour.

It was a very personal shot, and involved two innocent parties in Kyrgios's great friend Kokkinakis, and Wawrinka's girlfriend. Whether or not Wawrinka understood it on the spot (given he may have been in his bubble during a tight match, the fact that Wawrinka is French-speaking, and Kyrgios's heavy Australian accent, that's not a given), he certainly heard about it after the match.

In case some of the fans down near the court Wednesday night didn't hear it, Kyrgios repeated it, in a sort of "muttering to himself" kind of way.

Wawrinka retired down 6-7 (8), 6-3, 4-0 after feeling sharp pains in the left part of his lower back.

Kyrgios was asked about it after the match by Arash Madani of Sportsnet.

"He was getting a bit lippy at me, so I don't know, It was in the moment stuff sort of stuff. I don't really know; I just said it."

Afterwards, he expanded a little on that, but not much.

The exchange was all over social media even during the match. And the reaction was swift from all corners, beginning with Wawrinka's coach Magnus Norman.

Afterwards, a visibly downcast Wawrinka, who said some sharp pain in the left part of his lower back was the reason for his retirement, had some strong words for both Kyrgios, and the need for the ATP Tour to come down strongly on him.

In his interview, Kyrgios scoffed at the question about whether or not the two had spoken in the locker room.

Wawrinka had a rather different version of the post-match events.

Some two hours later, Wawrinka was still up, and shared some thoughts on Twitter, in English.

Clearly, as the time passed, the incident upset him more and more.

The question now is what, if anything, the ATP will do about it. Kyrgios is one of the rising young stars on the circuit, a charismatic, popular performer whose previous antics have, by and large, been dismissed because of his youth and because that was "his personality."

That's true, of course.

Meanwhile, Wawrinka is one of the ATP Tour's respected elder statesman now, a two-time Grand Slam champion.

But the subtle enabling of the behaviour may have created a situation in which that behaviour, unchecked, escalated. And Kyrgios crossed that line Wednesday night in Montreal.

Kyrgios's older brother Christos quickly weighed in:

So did his mother, Nill.

Later, after this story was posted, brother Christos opened another door.

The story, it seems, is just beginning.