Nick Kyrgios believes his journey from an overweight child playing on shabby public courts to the verge of a shock Wimbledon title can inspire all "outcasts".

The maverick Australian will become one of the All England Club's most controversial champions if he beats six-time winner Novak Djokovic in Sunday's final.

The 27-year-old, playing in his first major final, admitted he was having sleepless nights ahead of the showdown.

As he filled time counting down to Sunday, he posted a photo of himself as a self-conscious, overweight child, posing awkwardly with racquet in hand.

"I think that's just a strong message for any kid who doubts himself. Just keep going. Look at that photo, I literally look like Manny from 'Modern Family'," he said, referring to the hit US comedy series.

"I grew up in Canberra, the courts I trained on were horrible, and now I'm in the Wimbledon final. 

"I think it's honestly an inspiration for any kid who's kind of been outcast or just surrounded by negative headlines or just being brought down from a lot of different angles."

Kyrgios's career has been one of more downs than ups, a journey marked by a series of bust-ups with players, officials and even fans.

Until this Wimbledon, he only had two Slam quarter-final runs to his name, the last of which was the Australian Open in 2015.

The first was his maiden appearance at Wimbledon in 2014 as a teenage, 144th-ranked wild card, shocking Rafael Nadal in the fourth round.

Even Kyrgios admits he thought his time had come and gone.

"You just have to ride the waves, roll with the punches in a Grand Slam," he said.

"There's definitely times where I hate this sport, but there are times where I think I'm one of the most competitive people I've ever met."

Despite fines totalling $14,000, admitting spitting in the direction of the crowd and even getting accused of being a "bully" by Stefanos Tsitsipas, Kyrgios has been winning fans at this year's tournament.

Even John McEnroe, former Grand Slam-winning bad boy turned respected TV commentator, is warming to the Kyrgios show.

"He's being professional, I love it. He's one of the smartest people I've ever seen, on and off the court," the American told the BBC.

If he wins on Sunday, Kyrgios does not see himself as a natural heir to Djokovic, Rafael Nadal and Roger Federer, who have mopped up 62 Slam titles between them.

"Please don't put the pressure on me to do another one. Federer, Nadal, Djokovic, these guys are so rare."