Andy Murray was all smiles following his heroic victory against Thanasi Kokkinakis on Thursday night - and then displayed his very cheeky sense of humour.

Murray, 35, was asked post-match by Channel 9's John Fitzgerald how he managed to claw his way back from the brink, down two sets to love and staring elimination from the Australian Open in the face.

He responded he has a 'big heart', which was an understatement given the manner in which he found a way to win.

When Aussie tennis legend Fitzgerald suggested 'Well if I may say, I think you have big everything I think.'

The 35-year-old, who has already spent 10 hours on court after consecutive five-set victories at Melbourne Park, playfully responded: 'I'm not sure my wife (Kim) would agree.'

Fitzgerald later joked Murray was a 'strange guy', which the British veteran agreed with, stating 'my wife often says that.'

Speaking at his press conference, Murray reaffirmed his belief his round two clash against Kokkinakis finished far too late - 4.05am local time.

'I don't know who it's beneficial for,' he stated. 'It ends in a bit of a farce.

'Amazingly, people stayed until the end, and I really appreciate them doing that and creating an atmosphere for us at the end.

'Some people obviously need to work the following day and everything. 

'If my child was a ball kid for a tournament and they're coming home at five in the morning, as a parent, I'm snapping at that.

'It's not beneficial for them. It's not beneficial for the umpires, the officials. I don't think it's amazing for the fans. It's not good for the players.'

Murray was also furious during his match with Kokkinakis when he was denied a request for a toilet break early in the fifth set as he had exceeded his 'allocation'.

The three-time Grand Slam winner asked to use the bathroom - but his plea fell on deaf ears.

He next faces 24th seed Roberto Bautista Agut for a spot in the fourth round on Saturday.