Nick Kyrgios has revealed he decided to skip the inaugural United Cup as he wants to give himself the best chance of recovering from an injury ahead of the Australian Open.

The 27-year-old sparked controversy on Wednesday, when he pulled out of Australia's first match of the tournament after struggling to recover from an ankle injury he suffered in Dubai last week.

Kyrgios was scheduled to spearhead the Australian team, starting against Great Britain's Cameron Norrie in Sydney on Thursday night, but withdrew from the mixed-gender tournament ahead of Wednesday's team press conference.

The world No22 was also due to play Rafael Nadal in the most eagerly-anticipated match-up of the event when Australia meets Spain next week.

His late withdrawal has left Australia in the lurch, and his teammates only learned 10 minutes before their press conference that he would no longer be joining them. 

But Kyrgios has since looked to set the record straight, explaining his withdrawal was motivated by his desire to give himself the best possible chance to win the Australian Open next month.

'Winning a match at a grand slam level is not an easy task,' he told The Age on Thursday. 

'People underestimate the pressure and the nerves with being a part of one of the biggest tournaments of the year.

'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 trained on the courts at Sydney Olympic Park on Tuesday to test out his injured ankle, which he injured at an exhibition tournament last week. 

And he said informed Tennis Australia chief executive Craig Tiley and United Cup tournament director Stephen Farrow of his potential withdrawal before it was made official.

For their part, both Tiley and Farrow have defended Kyrgios, insisting there were no reasons to doubt his ankle issue was a genuine injury.

'We all worked together to try and get the best outcome,' Kyrgios said. 

'Not everyone is going to understand or see it from my side and that is okay. 

'What my team and I can control is how we go about our business and make sure who needs to know, knows - and we leave it at that.

'It is obviously very difficult. It’s not ideal to have an injury at any time in the season, but that is the risk I run every time I step on court.'

But Australian team captain Lleyton Hewitt has hit out at a 'lack of communication' over Kyrgios' controversial withdrawal.  

The latter was replaced by Alex De Minaur, who lost to Norrie in straight sets at the Ken Rosewall Arena in Sydney. 

De Minaur, who was expected to face Britain's Dan Evans and Spain's Pablo Curreno Busta, will also face Nadal next week. It is a significant change as both Norrie and Nadal are left-handed, while Evans and Curreno Busta are right-handed.

'I was in the same boat as all the other players yesterday, I didn’t know anymore,' Hewitt said.

'So it was pretty tough for everyone. It was more the lack of communication I think, for these guys not knowing.

'For the whole team, it was pretty tough not knowing what was going on for the last 24 hours. It’s more the communication, and if it was just worrying Nick, that’s one thing.'

Hewitt added he had to wait 'a little while' to receive a response from Kyrgios. Asked how communication could be improved, he replied: 'Just responding, that’s the normal way of doing it.'