World number one Novak Djokovic says he will apologise to a ball girl after appearing to shout at her during his fourth-round match with Kevin Anderson.
Djokovic vented his anger in the girl's direction before going on to secure a 6-7 (6-8) 6-7 (6-8) 6-1 6-4 7-5 win.
"I'm sorry. There was nothing towards her. Maybe she was just afraid of my screaming there," Djokovic said.
"I was pretty close to her. I'm definitely going to try to apologise to her if I did something wrong."
Defending champion Djokovic had to play the final set against South African Anderson on Tuesday after bad light halted the contest at two sets apiece the previous evening.
He next faces ninth seed Marin Cilic in the quarter-finals on Wednesday.