On Wednesday, Kyrgios stunned Nadal in the Mexican Open as he won 3-6 7-6 7-6 in a match that took over three hours.
Whilst serving, Kyrgios attempted to take advantage of Nadal’s deep position and hit an underarm serve, which missed the service box.
The incident clearly rattled Nadal, who said Kyrgios “lacks respect for the public, the rival and towards himself”.
However, Kyrgios was unapologetic saying: “I’m different, Rafa’s different, he can focus on what he needs to do.
“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.
“It’s the way I play, it’s the way he plays.
“He’s very slow between points. There’s a rule in the books that says you have to play at the speed of the server, Rafa has the speed every time.
“I’m not going to comment on his game, he has his game, I have my game.”
While Roger Federer appeared to give his support for Kyrgios adding: “Yeah, underarm is definitely a tactic, I believe.
“Especially when guys are hugging the fence in the back. From that standpoint, shouldn’t be ashamed if you try it out. Just look silly if you miss it sometimes.
“Why not try it? The problem is like in practice, you never really try it.
“When you come out in the big stage in front of a full crowd, tricky to pull off.”
But speaking on the Beyond The Baseline podcast, Anderson, the world number five admitted he would hit underarm serves if he “perfected” it but did feel the tactic won’t be accepted by those in tennis.
Anderson said: “It’s funny how there is an unwritten rule or code that deems the underhand serve not sportsmanlike.
“I’ve played a few guys when they return from extremely far back, I sometimes think if that is something I can perfect it would be something worth bringing out.
“But I guess it is one those things that is not accepted by the tennis world.”