Sam Stosur's hopes of progressing deep into the Sydney International received a boost with the withdrawal of her potential second-round opponent, Agnieszka Radwanska.
The world No.5, who won last year's season-ending WTA Tour finals in Singapore, pulled out after less than 24 hours after winning the Shenzen Open in China on Saturday, citing an injured left leg.
Stosur will take on beaten US Open finalist Roberta Vinci in the first round, with the winner to play veteran Daniela Hantuchova instead of Radwanska.
Defending women's champion and world No.6 Petra Kvitova (illness) also pulled out for the second time in the new year. The Czech retired from the first round of the Shenzen Open with a stomach virus.
The withdrawals continue a concerning build-up to the Australian Open for the game's leading women's players.
World No.1 Serena Williams pulled out of the Hopman Cup with a knee injury, while No.2 Simona Halep (Achilles), No.3 Garbine Muguruza (foot) and No.4 Maria Sharapova (forearm) all withdrew from the Brisbane International with injuries.
That tournament was eventually taken out by former world No.1 Victoria Azarenka, who beat Angelique Kerber 6-3 6-1 to claim her first title since 2013.
In Sydney, 2014 champion Tsvetana Pironkova continued her love affair with the tournament, upsetting Lesia Tsurenko to progress to the second round.
Two years ago she came through qualifying to win eight straight matches, including three against opponents ranked inside the world's top 10. Last year she also got through qualifying before reaching the semi-finals.
This time the world No.59 was given a wildcard.
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