World number 22 Kyrgios, who enjoyed a superb 2022 winning the Australian Open men's doubles title and finishing runner-up to Novak Djokovic in the Wimbledon final, pulled out of the joint ATP and WTA event on Wednesday with an injury.

Hewitt said on Thursday that he had been unaware of Kyrgios' withdrawal until the player's announcement and expressed frustration over his lack of communication.

On Friday, Australia's Ajla Tomljanovic pulled out of her match against Britain's Harriet Dart due to a left knee injury and Kyrgios responded to a Twitter post wondering if she would be treated similarly by co-captain Sam Stosur.

"Mmm I wonder if Stosur will throw her under the bus like our captain did for me...'hard to prepare when you don't know what's going on'," Kyrgios said.

Kyrgios, who opted out of Australia's Davis Cup team this year, said he had been in communication with Tennis Australia chief executive Craig Tiley as well as United Cup tournament director Stephen Farrow about his injury.

The mercurial Australian trained on the practice courts at Sydney Olympic Park on Friday. The Australian Open begins on January 16.