Gael Monfils has withdrawn from the Hopman Cup mixed team event due to an unspecified leg injury and will be replaced by French compatriot Kenny De Schepper.
It was not clear whether the injury would prevent the 24th-ranked Monfils from competing in the Australian Open beginning January 18 in Melbourne.
"It's unfortunate to hear Gael is unable to play in Perth. We wish him well over the next couple of weeks ahead of the Aussie Open," Hopman Cup tournament director Paul Kilderry said on Thursday.
De Schepper and his partner Caroline Garcia play their first match on Monday against the British team of Andy Murray and Heather Watson.
Serena Williams and Jack Sock open for the United States, also on Monday, against Elina Svitolina and Alexandr Dolgopolov of Ukraine.