World No.5 Agnieszka Radwanska is the latest big-name women’s player to pull out of the Sydney International, joining defending champion Petra Kvitova as an injury withdrawal.

Radwanska, who won the WTA’s Shenzhen Open title on Saturday, is carrying a left leg injury while Kvitova succumbed to a gastrointestinal illness the world No.6 picked up in China last week.

“I’m really disappointed to have to withdraw from the Apia International Sydney but unfortunately I am still not feeling well,” Kvitova said in a statement on Sunday.

The two withdrawals continue a troubled build-up to this month’s Australian Open for a number of leading contenders, including world No.1 Serena Williams (knee), No.2 Simona Halep (achilles), No.3 Garbine Muguruza (foot) and No.4 Maria Sharapova (forearm).

Australian No.1 Sam Stosur is also battling a wrist problem.

World No.10 Angelique Kerber is the only member of the top ten to not withdraw, lose first round, or retire through the first few weeks of the 2016 season.

Earlier on day one in Sydney, 2014 champion Tsvetana Pironkova upset Lesia Tsurenko 7-6 6-2 to move to the second round, where she’ll be joined by dual Wimbledon champ Svetlana Kuznetsova, who lost just two games in a 6-2 6-0 romp over Australian wildcard Tammi Patterson.

Former world No.1 Jelena Jankovic rebounded from a first-round exit in Brisbane to score a 6-3 6-4 win over American Coco Vandeweghe.