World No.1 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.

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.”

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.”

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.”