Former Australian Open champions Naomi Osaka and Victoria Azarenka withdrew from their warm-up tournaments for the year's first Grand Slam on Saturday, citing injuries.
Osaka pulled out of her Gippsland Trophy semi-final with an unspecified "niggling injury" but said she looked forward to competing at the Australian Open which starts on Monday.
"Sorry to Tennis Australia and the fans to have to withdraw today," Osaka said in statement tweeted by the WTA.
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"I have a niggling injury and in light of the AO on the horizon, I need to be cautious. I look forward to competing next week."
Belgian Elise Mertens has a walkover to the final of the Gippsland Trophy.
Azarenka, who won back-to-back Australian Open titles in 2012-13, withdrew from her Grampians Trophy quarter-final against Annett Kontaveit, giving the Estonian a walkover to the semi-finals.
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The WTA said the Belarusian had a lower back problem.
The injuries are a further blow for organisers, coming a day after Serena Williams withdrew from her semi-final against world number one Ash Barty.
Third-seeded Osaka faces former quarter-finalist Anastasia Pavlyuchenkova in the first round of the Australian Open, while 12th seed Azarenka is scheduled to meet American Jessica Pegula.
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