Naomi Osaka and Victoria Azarenka withdrew from their respective tournaments on Saturday due to injuries.
Osaka, a three-time grand slam champion, opted out of her Gippsland Trophy semi-final against Elise Mertens.
Azarenka, meanwhile, was due to face Anett Kontaveit in the Grampians Trophy quarter-finals.
Osaka said her move was a cautious one ahead of the Australian Open, which begins on Monday.
"Sorry to Tennis Australia and the fans to have to withdraw today," she said, via the WTA.
"I have a niggling injury and in light of the Australian Open on the horizon, I need to be cautious. I look forward to competing next week."
It continues what has been a difficult build-up to the first grand slam of the year.
On Friday, Serena Williams withdrew from her semi-final at the Yarra Valley Classic due to a right shoulder injury.
It comes amid a busy schedule for players after Thursday's action was called off due to a coronavirus scare.