Nick Kyrgios' girlfriend posts emotional message after star's defeat at Australian Open

After sealing the win, he said on-court: "I came to win this match and I am happy that I managed to do it," he said.

"That's the only choice when you are booed between first and second serves."

Right on cue, that incited a real smattering of boos from the crowd, before he was told that the noise from earlier had actually been the "siuu" noise made popular by football megastar Cristiano Ronaldo.

"What I'm saying is, between first and second serve. It's not easy," he responded, standing by his views.

He later had another dig at the crowd in an interview with Eurosport, in which he claimed those who had been making noise between points "probably have a low IQ".