Costeen Hatzi was left mortified when Nick Kyrgios showed off his urine during a hilarious behind-the-scenes moment captured by Netflix's cameras.

Kyrgios, 27, stars in the first episode of Break Point, tennis' answer to Drive To Survive which aired on Friday. 

A camera crew followed the tennis superstar during his campaign at last year's Australian Open. Despite being knocked out of the men's singles in the second round, Kyrgios and close friend Thanasi Kokkinakis took the doubles crown. 

And, shortly after the pair's semi-final victory in Melbourne, Netflix has revealed how Kyrgios was called in for a drugs test - which tennis stars are subjected to regularly throughout the year.

However, during a FaceTime call with girlfriend Hatzi, viewers discover that Kyrgios was struggling to provide the requisite amount of liquid for the drug testers.

'Theyre just doing a urine test,' Hatzi explains. 'He's like 30ml under, so he has to keep drinking water.'

Then, Netflix captures a FaceTime call between Kyrgios and his girlfriend - who met when he inquired to buy a mirror from her off Instagram.

'You need to just scull the water,' she tells him.

'I'm trying baby,' Kyrgios responds. 'I've sculled two waters, one pepsi, one juice. I'm trying.' 

'Well, just do your best,' Hatzi says.

Kyrgios then flips the camera, showing the amount of urine he has produced for the drug testers. 

A horrified Hatzi exclaims: 'Ew, don't show me the pee!'

Kyrgios replies: 'I'm doing my best, I'll be there as soon as I can.'

Turning to the camera crew, Hatzi says: 'Yeah, he definitely needs to drink more water, because it wasn't looking too good.' 

Hatzi plays a significant role in Kyrgios's episode, titled The Maverick. The pair had only been dating for two-and-a-half months when they were joined by Netflix, and Hatzi admitted to not knowing anything about tennis when they met.

'We've been together about two and a half months,' Hatzi says. 'We met online and we've been hanging out every day since.'

Hatzi also opened up on her relationship with Kyrgios, insisting that he is not as wild as he appears on court.

'He's not as crazy as everyone thinks he is. I never really watched a tennis game in my life so this is all new for me.' 

Prior to Kyrgios's first round match against Liam Broady, the Australian's manager, Daniel Horsfall, is seen explaining the scoring system to Hatzi. 

'If you've never seen a tennis score before, it can be confusing,' he says. 'It's a five-set match, but in every set, six games make a set. So it's basically first to six.'

Kyrgios went onto enjoy his best year in tennis, reaching the Wimbledon final before losing out to Novak Djokovic, and recently said that Hatzi is his 'secret weapon'.