Rafael Nadal plants kiss on ball girl in beautiful moment at Australian Open

Rafael Nadal has sealed a third-round Australian Open berth with a kiss on the cheek for a ballgirl who felt the wrath of his famous forehand.

The Spanish legend, hunting a record-equalling 20th grand slam title at Melbourne Park, brushed aside determined Argentine Federico Delbonis 6-3 7-6 (7-5) 6-1.

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But as he honed in on the straight-sets win on Thursday night, Nadal inadvertently struck a wayward shot into the head of a ballgirl while stretching for a Delbonis serve at 4-1 in the third set.

Nadal rushed to check on the child's well-being and even planted a peck on her cheek after she gave him a 'thumbs up' to confirm she was OK.

"I was so scared for her," he said post-match.

"The ball was quick and straight on her. Super brave girl."

The beautiful moment sent fans into a frenzy.

Spurned break point chances from Nadal - who converted just three of 20 on Delbonis' serve - dragged the Rod Laver Arena clash out to two-and-a-half hours.

"I lost a lot of opportunities on break points," Nadal said as he extended his career record over Delbonis to 4-0.

"I found a way to finally win that second set and in the third, I think I played a little bit more relaxed."

Nadal dismisses Kyrgios antics

Countryman Pablo Carreno Busta now awaits Nadal in the last 32 before a potential mouth-watering fourth-round meeting with local hope Nick Kyrgios.

The duo have long-butted heads and Kyrgios may have stoked the flames of their discontent by mimicking Nadal's serve during his second-round win over French journeyman Gilles Simon.

"I really don't care," Nadal tersely told a journalist when informed of Kyrgios' impression.

"I am here to play tennis. Honestly, I don't care at all. If was funny, good."

Kyrgios was coasting to a routine second-round win over Simon, but as the finish line approached - up 4-2 with the break in the third set - the 23rd seed lost his way.

Two straight double faults from Kyrgios handed Simon a lifeline, with the former world No.6 gratefully accepting to force a fourth set.

In the aftermath, the Aussie directed his fury toward his player's box, which included Davis Cup captain Lleyton Hewitt.

"Of all the things you could say on break point, 'stay tough'," he bellowed.

"That's what I get, every break point, 'stay tough' ... wow.

"So creative, so creative."

But rather than let the blip become a full-blown meltdown, Kyrgios hit the reset button to bounce back and score a 6-2 6-4 4-6 7-5 victory.

"I just put my head down," Kyrgios said.

"I lost my way a little bit in the third set. I put my head down, I told myself 'just cut the bulls*** and just get to work'.

"I got the break at five-all. It was a good feeling to get through that."