Nick Kyrgios took a cheeky dig at his critics after tickets for Friday's practice match with Serb Novak Djokovic sold out in 58 minutes, proving the Australian's huge box office draw.

Nick Kyrgios said he withdrew from the inaugural edition of the United Cup to be in peak condition for next month's Australian Open, adding that he did not expect everyone to understand the reasoning behind his decision.

Nick Kyrgios was fined $14,000 on Wednesday for his spectacular double racquet smashing tantrum at the end of his US Open defeat to Karen Khachanov.

Just when tennis fans thought Nick Kyrgios had run out of ways to surprise them, the Australian came up with another bizarre shot during a rally against Daniil Medvedev at the U.S. Open on Sunday.

Danill Medvedev said Nick Kyrgios is playing at such a high level that he merits comparison with Grand Slam heavyweights Novak Djokovic and Rafael Nadal.

Australia's Nick Kyrgios sent defending champion Daniil Medvedev tumbling out of the US Open on Sunday as US teenager Coco Gauff reached the quarter-finals for the first time.

Fiery Australian Nick Kyrgios has been fined $7,500 for "spitting and audible obscenities" during his second-round win at the U.S. Open on Wednesday, tournament organizers told Reuters.

Australian Nick Kyrgios produced another extraordinary performance to demolish compatriot Alex de Minaur 6-2 6-3 at the Canadian Masters on Thursday, a day after stunning world number one Daniil Medvedev.

Wimbledon runner-up Nick Kyrgios has been handed a wildcard into next month's U.S. Open tune-up event in Cincinnati, Ohio, organisers of the Western & Southern Open said on Monday.

Australia's Davis Cup captain Lleyton Hewitt said he told Nick Kyrgios he should be proud of his runner-up finish at Wimbledon and hopes he will play for the national team.

Nick Kyrgios did not disappoint in his maiden Grand slam final as the Australian brought his extraordinary brand of improvised tennis theatre to the world's greatest tennis stage on Sunday.

Novak Djokovic said he would make good on his deal to buy Nick Kyrgios drinks and dinner after beating the Australian to claim a fourth successive Wimbledon title on Sunday.

Nick Kyrgios has lived up to his reputation as one of the bad boys of tennis at Wimbledon but he is just the latest in a long line of controversial characters. The Australian, who takes on Novak Djokovic in Sunday's men's final, has made waves at the All England Club this year with his antics, including spitting in the direction of fans and calling for third-round opponent Stefanos Tsitsipas to be disqualified.

Nick Kyrgios forgot how important family was as his life spiralled into chaos, but sibling Christos told Australian media Sunday he has finally "got my baby brother back".

The pair met each other at practice and had a word before taking the conversation to Instagram for their millions of followers.

Nick Kyrgios' bad boy image is in many ways a "stage persona", a way of protecting the "sweet, genuine, sensitive person" inside, the player's former manager and agent has told Australian media.

Nick Kyrgios has told Rafael Nadal that he hopes the Spaniard's "recovery goes well" after the 22-time Grand Slam title winner was forced to withdraw from their Wimbledon semi-final.

Nick Kyrgios reached the first Grand Slam semi-final of his chequered career with a comfortable 6-4 6-3 7-6(5) victory over Chile's Cristian Garin at Wimbledon on Wednesday.

An angelic Nick Kyrgios reached his first Grand Slam quarter-final for seven years when he recovered from a slow start to beat steady American Brandon Nakashima in five sets on Wimbledon's Centre Court on Monday.

Greek fourth seed Stefanos Tsitsipas labelled Nick Kyrgios a "bully" with "an evil side" to his character after losing a bad-tempered Wimbledon third-round clash on Saturday.