Novak Djokovic came within a few centimetres of the second default of his career as he narrowly avoided smacking a ball girl with a ball.

Towards the end of the second set of his third-round match with Botic van de Zandschulp, Djokovic lashed at a ball in fury. It flew towards the ball girl crouched by the net post and came within a whisker of hitting her in the head.

Had it done so, umpire John Blom would have had no choice but to throw Djokovic out of the tournament - the same fate he suffered at the US Open in 2020 when he hit a line judge with a ball.

Those two incidents make tennis's rules on the subject appear very silly, in the sense that they are totally based on outcome.

What Djokovic did in Melbourne was far more dangerous than the act that got him chucked out in New York. He hit the ball far harder - it could have done the ball girl serious damage, which was never a possibility with the US Open line judge.

Djokovic gave a cursory apology and got on with things, in a generally bad-tempered second half of this match as he began to struggle with his right ankle and blisters on his feet.

At time of writing, he was two sets up, at 3-3 in the third, as he chases an 11th Australian Open title.

The incident shocked former British No 1 Tim Henman in his role as a commentator on TNT Sports' coverage of the Australian Open.

'Oh my goodness,' Henman said as the incident unfolded on the broadcast.

He and colleague Nick Lester suggested Djokovic would be avoiding eye contact with the chair umpire after the near miss.

The incident could have brought down the curtain on a final shot at the Australian title for 38-year-old Djokovic.

His first week in Melbourne has already been controversial after his wife spoke out about Naomi Osaka and her conduct.

Osaka's tense victory over Sorana Cirstea on Margaret Court Arena ended with a frosty exchange at the net and visible agitation from Osaka during her on-court interview. She later apologised.

Jelena Djokovic weighed in on social media, questioning whether Osaka's conduct between serves should have been penalised.

'Hm, I'm surprised that this is not being called hindrance,' Mrs Djokovic wrote.

'In between two serves, when crowds are applauding or shouting, the chair ump asks not to shout between serves as it is disturbing to the player.'

'The point is not finished. Sorana missed her first serve and is focusing on getting in the second, it is a slight pause. And it is disrespectful to applaud at someone's first serve mistake too.'

She also questioned the officiating, writing: 'I am surprised that the chair / Naomi thought that was fair?! Were there any rule changes that I missed?!'