Nick Kyrgios left his fellow competitors astounded on Wednesday after abruptly withdrawing from the United Cup the very day before the competition was set to start, shortly after Rafael Nadal had commented on the Australian's potential to take home a Grand Slam title given his "all the weapons" arsenal.
The temperamental star withdrew ahead of the new mixed-teams event in Sydney, Brisbane and Perth, depriving fans of a scheduled clash between him and the Spanish great.
Instead, Alex de Minaur will face Nadal in a round-robin singles match.
Australia co-captain Sam Stosur said they only learned about Kyrgios' withdrawal minutes before a scheduled team press conference.
"We just found out," she said. "We move forward now and do our best on the day."
The Sydney Morning Herald cited the Kyrgios camp as saying he suffered an ankle injury during an exhibition tournament in Dubai last week.
They added that he practiced in Sydney on Tuesday before deciding against competing in the United Cup.
His on-court behavior has often betrayed Kyrios,' but he had a stellar season this year, reaching his first Grand Slam final at Wimbledon, losing to Novak Djokovic.
He was agonizingly beaten in five sets in the U.S. Open quarter-finals by Russia's Karen Khachanov.
Before Kyrgios pulled out of the United Cup, Nadal, who has 22 Grand Slam titles, said the Australian could quickly go all the way.
The Australian Open next month will be his first opportunity of the year, a tournament where the Spaniard is defending champion.
"I know he doesn't like a lot to play Roland Garros; that's the only tournament that looks like he doesn't like to play that much," said Nadal in Sydney.
"The rest of the tournaments, he played final in Wimbledon, in New York, he was close with the quarter-finals, I think, with a very positive chance.
"He can win in any tournament that he's playing. He has all the talent, and the weapons to win against any player. Of course, he can."
Kyrgios told reporters earlier this week that he was "training well, enjoying it, mentally feeling good. That's all that matters."
The Australian Open gets underway at Melbourne Park on Jan. 16.