Cape Town - Former Australian tennis professional Sam Groth reckons he knows why Rafael Nadal isn't a fan of Nick Kyrgios.

Things got quite heated between Nadal and Kyrgios during their recent round of 16 match at the Mexican Open, with the Australian coming out on top with a 3-6, 7-6 (7/2), 7-6 (8/6) win.

Kyrgios threw in an underarm serve during the match and when his victory was confirmed he fell to the floor in celebration. Once the Australian got up he stuck his finger behind his ear, which seemingly didn't go down well with the 17-time Grand Slam winner.

After the match Nadal accused of the 23-year-old Kyrgios of being "disrespectful", saying: "He could win Grand Slams and fight the top positions of the ranking, but there is a reason why he is where he is.

"He lacks respect for the public, the rival and towards himself."

Kyrgios defended himself.

"That's the way I play. That's the way he plays, he's very slow between points and the rule of the book says you have to play at the speed of the server," he said.

Groth, though, feels the fact that Kyrgios' head-to-head of 3-3 against Nadal is the reason for the Spaniard’s tetchiness.

"I don't think Rafa really likes Nick very much," he told RSN radio. "Nick burst onto the scene beating Rafa at Wimbledon so I think there's probably been something there from day one.

"To be honest, they're 3-3 head-to-head now and I don’t think there are too many guys in the world Nadal would have a 50-50 record against.

"He probably just doesn't like it very much."