Fritz defeated Nikoloz Basilashvili from Georgia 6-4 6-2 4-6 7-5 at John Cain Arena on Tuesday.

It is tradition for winning players to write a message on the camera at the end of their match, but viewers were quick to say the 25-year-old’s choice looked hilariously inappropriate.

Some took to social media to ask the men’s World No. 9 to explain the “NSFW drawing”, which had been broadcast across the world.

In response, Fritz tweeted: “For ur information i was trying to draw a (lock) emoji…. I just forgot the very important fact that I suck at drawing.”

Fritz’ victory on Tuesday happened under a closed roof as the Australian Open’s extreme heat policy was activated.

The roof was also closed at Rod Laver Arena and Margaret Court Arena, while play was suspended on other outside courts until 5pm.

The policy was activated when the tournament’s heat stress scale reached five. The scale takes into account air temperature, the strength of the sun, humidity and wind speed.

But Fritz said the dry Melbourne heat did not bother him.

“It’s hot, but it’s dry heat, so I don’t really mind it too much,” he said at a press conference after the match.

“I think playing in, like, D.C. last year, US Open some years, is much worse because it’s so hot, plus the humidity.

“When it’s like today, it’s not that humid … I don’t think it’s as bad.”

Fritz was also asked how he felt about “the Netflix curse”, referring to the unfortunate events that have followed players who appeared in the new documentary series Break Point.

Australia’s Nick Kyrgios and Ajla Tomljanović, and Spain’s Paula Badosa, who star in the five episodes out on Netflix, have had to pull out of the Australian Open.

While the internet may have dubbed it “the Netflix curse”, Fritz was unaware it was a thing.

“I noticed the people pulling out of the tournament, but I didn’t know it was a thing, like ‘I’m going to lose my first round because I’m in the Netflix show,’” he said.

He added with a smile: “I didn’t think of that.”