Roger Federer has dropped out of the ATP Cup in January, meaning there will be no showdown with Andy Murray.
The 38-year-old, currently ranked three in the world, had committed to playing the inaugural tournament in Australia at the start of 2020, but has opted out in order to spend more time with his family.
The team competition sees 24 countries compete against each other – initially in a round-robin group stage – and Federer's Switzerland side were scheduled to start their campaign against Murray's Great Britain in Sydney on January 3.
It would have been the first meeting between the two since a semi-final in Cincinnati four years ago.
But with the veteran desperate to try and win a maiden Olympic gold medal in Tokyo in August, he is keen to keep himself fresh.
"It is with great regret that I am withdrawing from the inaugural ATP Cup event," said Federer on the tournament's official website.
"When I entered the event last month, it was a really difficult decision because it meant less time at home with the family and a fully intense start to the season.
"After much discussion with both my family and my team about the year ahead, I have decided that the extra two weeks at home will be beneficial for both my family and my tennis.
"It pains me to not be a part of the most exciting new event on the calendar. But this is the right thing to do if I want to continue to play for a longer period of time on the ATP Tour.
"I am sorry for any inconvenience or disappointment my withdrawal may cause for the fans, but I hope you can understand why I made it.
"For my Australian fans, I look forward to seeing you all at the Australian Open, fresh and ready to go."
As a result of his withdrawal, Switzerland drop out of the tournament as they only qualified due to Federer's ranking.
