Kyrgios' late United Cup withdrawal surprises Australia team mates

Kyrgios, who is ranked 22nd in the world, was set to lead Australia in the joint ATP and WTA event, which is being held in Sydney, Brisbane and Perth and offers ranking points and $15 million in prize-money.

Organisers said the Wimbledon finalist, who was due to face Britain's Cameron Norrie in his first singles match on Thursday in Group D, withdrew due to injury.

"We literally just found out 10 minutes ago. Obviously it's news to all of us and we just move forward now," co-captain Sam Stosur told reporters.

Kyrgios, who opted out of Australia's Davis Cup team this year, later posted a video on Instagram where he was seen out in the sunshine at a harbour with the caption 'Beautiful day'.

Alex de Minaur, who will now move into the number one men's position for Team Australia, wanted to avoid discussing Kyrgios and focus on the upcoming event.

"I think it would be great if we just talk about this great team," he said. "We are all here, we are all happy to be here, we are about to play an exciting new event, something new for all of us - the United Cup."

Australia will also play Rafael Nadal's Spain in Group D.

The tournament, which runs from December 29th-January 8th, features 18 countries split into six groups of three, with teams playing two men's and two women's singles matches and a mixed doubles match.