Nick Kyrgios makes locker room 'fight' claim after winning Australian Open doubles match with Thanasi Kokkinakis

Nick Kyrgios, left, and Thanasi Kokkinakis were in party mode during their doubles match on Friday. (Getty Images: Darrian Traynor)

According to Nick Kyrgios, tennis is a "soft" sport.

Kyrgios made the assertion while claiming he and doubles partner Thanasi Kokkinakis were threatened with violence following their win over number one seeds Nikola Mektić and Mate Pavić at the Australian Open on Friday.

In what was an upset second-round win, Kyrgios and Kokkinakis defeated the Croatian pairing 7-6 (10-8), 6-3 in front of a boisterous crowd on Kia Arena.

The spectators enthusiastically got behind the Australians, who did their best to entertain the masses throughout the match with not only brilliant tennis, but more than the odd display of showmanship.

This did not go down well with Mektić and Pavić, who vented their frustration and even complained to the chair umpire about the behaviour on court. 

And it seems it was also not well received by their support team, if Kyrgios's version of events is anything to go by.

Kyrgios, left, and Kokkinakis knocked the number one seeds out of the tournament. (Getty Images: Darrian Traynor)

Kyrgios tweeted this morning a claim that a coach and trainer associated with the Croatians made a threat of violence after the match.

"Just letting you know after yesterday's chop fest in doubles my opponents coach and trainer proceeded to threaten to fight in the players gym," Kyrgios wrote.

"Tennis is a soft soft sport all because I moved and hit them with a tennis ball."

Kokkinakis likened the scene to a UFC bout.

"That was crazy!! Mans (sic) thought it was @ufc," Kokkinakis tweeted.

The crowd was in a festive mood during Friday's doubles match. (Getty Images: Darrian Traynor)

When Pavić and Mektić spoke to the media after Friday's match, they expressed their disgust with the crowd's "loud" behaviour.

Pavić also referred to Daniil Medvedev's comments about spectators making noise during his singles win over Kyrgios on Thursday night, when the Russian suggested they "probably have a low IQ".

"Obviously they cheer for Aussies," Pavić said.

"We saw yesterday also with Medvedev how it was. So, that's how they are here. We're used to that.

"But like I said, it wouldn't hurt them to show some respect."

Mektić and Pavić won the men's doubles title at Wimbledon last year and also claimed the gold medal in the event at the Tokyo Olympics.