(CNN) Rafael Nadal called it one of the more scary moments he's had on the tennis court.
The world No. 1 was en route to a straight-sets win against Argentina's Federico Delbonis, leading 4-1 in the third set of their second-round match Thursday.
But on a return of serve, a scorching forehand from Nadal hit a ball girl on the head.
There was an audible gasp from the crowd. Nadal grimaced.
"For her, probably it was not a good moment," the Spaniard said on court after the match. "I was so scared for her, honestly."
The girl gave him a thumbs up, but a still-concerned Nadal and Delbonis both went over to her to make sure that she was OK. Nadal lifted the girl's hat, gave her a kiss on the cheek and patted her on the head, drawing cheers from the crowd.
Nadal went on to win the match 6-3 7-6 (4) 6-1. He next will face fellow Spaniard and No. 27 seed Pablo Carreno Busta.
READ: Elliot Benchetrit hits back at critics over ball girl banana drama at Australian Open
After the win, Nadal went up to the ball girl again and handed her his headband.
"She's a super brave girl," Nadal said.
The Australian Open is the only major Nadal has won just once, back in 2009.