The Australian displayed some of his best form when beating Nadal in a tight three-setter at the Mexican Open on Wednesday in Acapulco but the high-quality spectacle didn't translate into positive words for the former world No.13.
There were several flashpoints in the match but Nadal appeared most incensed when Kyrgios complained about the time this year's Australian Open runner-up was taking between points on the Canberran's serve.
It prompted Nadal to say in a post-match media conference that Kyrgios should be fighting for grand slams under the No.1 ranking but "lacks respect for the crowd, his opponent and towards himself".
Responding after Nadal's comments, Kyrgios seemed non-plussed.
"I'm different. Rafa's different. He can focus on what he needs to do," Kyrgios said. "He doesn't know the journey I've been through. He doesn't know anything about me so I'm not going to listen at all."
Kyrgios, one of the fastest players on tour between points, then took aim at Nadal, who is among the slowest.
"It's the way I play. It's the way he plays - he's very slow between points and I think that the rule in the book is that you have to play to the speed of the server but Rafa has the speed every time," Kyrgios said.
"I'm not going to comment on him, his game. I've got my game; he's got his own game. We played well - that's the sport. People are different - I'm not going to take that into consideration at all."
A shot clock was introduced to tennis last year with a maximum of 25 seconds allowed between points, after the chair umpire's announcement of the score.
There might be more controversy ahead for Kyrgios in Friday's quarterfinal against Stan Wawrinka. The Australian made a crude remark about the Swiss veteran's girlfriend during a match at the 2015 Rogers Cup, a heated exchange allegedly taking place between the two tennis players in the locker-room post match.
Meanwhile, Australians Alex de Minaur and John Millman have also made the last eight in Acapulco.