CANBERRA - Controversial Australian tennis player Nick Kyrgios on Friday publicly apologized for comments he made during a tennis match against Swiss world Number 5, Stanislas Wawrinka.

Nick Kyrgios of Australia hits the ball against Fernando Verdasco of Spain (not pictured) during the Rogers Cup tennis tournament at Uniprix Stadium.[Photo/Agencies]

Kyrgios was subject to a backlash on social media following the unsavory quip he uttered during his match against Wawrinka at the Rogers Cup in Montreal.

Court microphones managed to pick up the Australian muttering, "Kokkinakis banged your girlfriend, sorry to tell you that mate."

The 20-year-old up-and-comer was referring to his close friend and fellow Australian Thanasi Kokkinakis who, at one time, had been romantically linked with Croatian teenager Donna Vekic, who is reportedly dating Wawrinka.

After the incident, which Kyrgios brushed off as comment made in the "heat of the moment", he was fined 10,000 U.S dollars by the ATP before he took to Facebook to apologize for his actions.

"I would like to take this opportunity to apologise for the comments I made during the match last night vs Stan Wawrinka," he said.

"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."

Following the outburst, Wawrinka took his shock to social media platform Twitter, where he said, "What was said I wouldn't say to my worst enemy. To stoop so low is not only unacceptable but also beyond belief."

Despite Kyrgios being lambasted by the world's media, Australia 's Davis Cup captain Wally Masur was quick to defend the incident, claiming it was nowhere near as bad as what the headlines had portrayed.

Masur said Kyrgios seemed to be talking to himself rather than to Wawrinka, who was on the opposite side of the court, waiting to return the next serve.

"When I actually saw the incident, what was fairly obvious is that Nick had his back turned to Stan, he was 90 feet away, and he mumbled it under his breath. No way was he actually being confrontational," Masur told Australia's Fox Sports on Friday morning.

"It's just a case of the court-side microphone, which is pretty amazing what it picked up, picked up the audio. It wasn't the scenario I had in my mind when I read the headlines."

However colleagues have labeled the outburst as yet another tantrum to add to the long list of on-court indiscretions that have overshadowed the prodigious player's recent form.

World Number 1 Novak Djokovic said the incident was "not fair" to Wawrinka, let alone Kokkinakis or Vekic who were not even present at the match.

"There's no excuse for what he has said," Djokovic said after a match on Thursday night.

"He was fined, he deserved it. I think he's going to learn a lesson in a hard way. Hopefully this won't happen to him anymore.

"I understand that every player goes through certain tantrums, emotional ups and downs during the match, but it's not fair, and there's no excuse of directing your tantrums to your opponent."

Also on Friday, Kyrgios' brother Christos was asked about the incident on morning radio in Sydney, but was cut off after he said a lewd remark relating to Kokkinakis and Vekic.

Meanwhile Kyrgios' mother told Fairfax Media that Kyrgios might have been incited by an incident that occurred earlier this year.

During a match at Queens that Wawrinka won in just 49 minutes, Wawrinka wrongly accused the Australian of faking an injury, and Nill Kyrgios said the bad blood between the two had obviously spilled over once again.

"If you give people lip then you've got to receive some back," she said on Friday.

"You know that Stan did say that Nick was faking an injury last time they played and Nick was actually very sick."

Early on Friday morning, Kyrgios faced a chorus of boos when he took to court against American John Isner. He lost the third-round match 7-5, 6-3.