Rafael Nadal accused Nick Kyrgios of lacking respect "for the public, the opponent and himself" after a stormy defeat to the Australian firebrand at the Mexico Open.
Kyrgios survived three match points to beat top-seeded Nadal 3-6, 7-6 (7/2), 7-6 (8/6) on Wednesday and reach the quarterfinals.
However, 17-time major winner Nadal was furious with Kyrgios who at one stage complained of being sick and served underarm late in the match before cupping his ear to the boos of the crowd at the conclusion of the second round tie.
"He is a player with huge talent and could be winning Grand Slams or fighting for the number one ranking," said Nadal. "But he lacks respect for the public, the opponent and for himself."
Kyrgios, ranked 72 in the world, hit back at Nadal.
"I'm different, Rafa's different. He can focus on what he needs to do. He doesn't know the journey I have been on, he doesn't know anything about me," said Kyrgios who famously stunned Nadal as a teenager at Wimbledon in 2014. "I am not going to listen at all. That's the way I play. The way he plays is very slow between points. I've got my game, he's got his game. People are different, that's the sport."
Kyrgios also defended his underarm serve on social media in response to a comment that said: "Praise for the underarm attempt. Someone will eventually catch Nadal out [for] standing so far back."
Kyrgios replied: "That's the only reason for doing it… I mean isn't that the idea to serve where the person can't get the ball? Try to get an ace?
Nadal had three chances to close out Wednesday's match after taking a 6-3 lead in the third-set tiebreaker. Kyrgios saved the first with a leaping drop shot, and the second with a net-skimming volley.
Nadal was just wide with a passing shot to make it 6-6, double-faulted to give Kyrgios a chance and sailed a backhand long to end the match after three hours and three minutes.
Kyrgios screamed and dropped to the court in celebration -- a conclusion that seemed unlikely when he complained to a trainer after the opening set that he was feeling ill but feared the fallout should he retire.