Novak Djokovic apologises for outburst

Novak Djokovic has apologised for yelling towards a ball girl during his fourth-round match with Kevin Anderson at Wimbledon.

The number one seed was forced to battle back from two sets down to reach the last eight, restoring parity on Monday night before finishing the job on Tuesday.

During the sixth game of the deciding set, Djokovic sent a forehand into the net and appeared to yell at a ball girl when demanding his towel.

However, the Serb has since apologised for his actions, which came during a "frustrating" period of the match for him.

"I'm sorry. There was nothing towards her. Maybe she was just afraid of my screaming there. I was pretty close to her. I'm definitely going to try to apologise to her if I did something wrong," Djokovic told reporters.

"Obviously the fifth set today was very frustrating, very tense. I didn't have basically any chances on his serve till the 11th game when he made two double faults and I made a couple of good returns from the forehand side. That was enough.

"Sometimes it's just good to scream and let it all out, because that's the way I work."

Djokovic will face Croatia's Marin Cilic in the quarter-finals.