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.
Kyrgios, who is ranked 22nd in the world, was set to lead Australia in the joint ATP and WTA event but withdrew from the tournament due to an injury on Wednesday, taking his own teammates by surprise with the late announcement.
"People underestimate the pressure and the nerves with being a part of one of the biggest tournaments of the year," Wimbledon runner-up Kyrgios told The Age and the Sydney Morning Herald in an interview published on Thursday.
"Throw in an injury and knowing you didn't give yourself the best chance only adds to the mountain of pressure you face. So feeling good physically is important."
Kyrgios added that he had been in communication with Tennis Australia chief executive Craig Tiley and United Cup tournament director Stephen Farrow about his injury.
"We all worked together to try and get the best outcome. Not everyone is going to understand or see it from my side and that is okay," Kyrgios said.
"I was working every day very closely with my team about my progression and speaking with William, my physio, after every session. I tried to be ready for it, but at some point, you need to listen to the advice you're receiving and do what is best."
Alex de Minaur, who moved into the number one men's position for Team Australia in place of Kyrgios, was beaten by Britain's Cameron Norrie on Thursday.
Speaking after De Minaur's defeat, Australia co-captain Lleyton Hewitt said he had also been unaware of Kyrgios' withdrawal until Wednesday.
When asked how Kyrgios could improve his communication, Hewitt told reporters, "probably just responding. That's the normal way of doing it. There was a little while (before he responded)."
"It's more just the communication. If it was just worrying Nick, that's one thing."
"When it revolves around the team and other people and their preparation to be playing the best they possibly can leading into the Australian Open, that's probably the hardest thing."
Meanwhile, Stefanos Tsitsipas battled back after losing the opening set to outlast Bulgarian Grigor Dimitrov 4-6, 6-2, 7-6(4) and give Greece a 2-0 lead on Thursday, the first day of the inaugural United Cup mixed team tournament in Perth.
Despina Papamichail earlier put Greece 1-0 up with a 3-6, 6-4, 6-1 win over Isabella Shinikova, and Maria Sakkari can seal the tie with victory over Viktoriya Tomova when Group A action resumes on Friday.
The $15 million tournament which replaces the short-lived ATP Cup men's team event as the 2023 season opener and concludes with the final in Sydney on Jan. 8, features 18 countries with ties played in Brisbane, Perth and Sydney.
Earlier, Taylor Fritz and Madison Keys began their build-up for next month's Australian Open with solid displays to give the United States a 2-0 lead over the Czech Republic in Sydney.
Fritz began with a 6-3, 6-4 win over Jiri Lehecka before Keys downed Marie Bouzkova 6-4 6-3 to put the Americans in control of the Group C tie.
"In a team event, the first match of the year, there are always some nerves, so it's great to come out and get the team ahead," said Fritz, who saved both break points he faced in the match.
The U.S. can expect a tougher challenge on day two as world number three Jessica Pegula takes on double Wimbledon champion Petra Kvitova. Frances Tiafoe will then face Tomas Machac.
A mixed doubles match would decide the tie if it was locked at 2-2.
In Brisbane, Italy and Brazil were tied at 1-1 in Group E after Lorenzo Musetti downed Felipe Meligeni Alves 6-3 6-4. Beatriz Haddad Maia earlier put the South Americans ahead with a 6-2, 6-0 win over Martina Trevisan.
Britain made a convincing start as Cameron Norrie eased past Australia's Alex de Minaur 6-3, 6-3 before Katie Swan doubled their advantage with a 6-4, 6-3 win over Zoe Hives.
"It is a tough task to play 'Demon' in Australia on this court, him playing at home. He loves playing here," Norrie said.
France took a 2-0 lead over Argentina after Alize Cornet and Arthur Rinderknech won their matches against Maria Carle and Francisco Cerundolo, while Switzerland have the upper hand in their tie against Kazakhstan thanks to wins by Belinda Bencic and Marc-Andrea Huesler.