BRISBANE, Australia -- It's been an injury and illness-filled start to 2016 for the top six women in tennis, and just a week from the start of the Australian Open.
Defending Sydney International champion Petra Kvitova, a two-time Wimbledon winner, pulled out of the Sydney tournament on Sunday, the second week in a row she's had to quit due to a stomach virus. She was joined a few hours later by Agnieszka Radwanska, the No. 2-seeded player in Sydney, who has a left leg injury.
Last week, the world's four top-ranked women retired or withdrew from tournaments due to injuries on the left side of their bodies: No. 1 Serena Williams (Hopman Cup/knee), second-ranked Halep (Brisbane/ankle), No. 3 Garbine Muguruza (Brisbane/foot) and fourth-ranked Maria Sharapova (Brisbane/forearm).
Now No. 5 Radwanska and No. 6 Kvitova are on the ever-growing injury list.
Kvitova retired during the first round of the Shenzhen Open in China last week. She was scheduled to play her first match in Sydney against Germany's Sabine Lisicki on Monday.
"I'm really disappointed to have to withdraw ... but unfortunately I am still not feeling well," the sixth-ranked Kvitova said in a statement.
Former No. 1 and now 16th-ranked Ana Ivanovic is healthy, but her new season is nonetheless off to a poor start. After losing in the first round last week in Auckland, she was granted a Sydney wild card.
Ivanovic, who won the French Open in 2008, months after losing the Australian Open final to Sharapova, was beaten 6-4, 6-2 by fifth-seeded Karolina Pliskova in a first-round match Sunday.
"I was thinking, it's not really (an) easy draw for first round," Pliskova said. "I was really expecting a tough match. I'm just happy it went a little bit more my way."
In other first-round matches, another Serbian former No. 1, Jelena Jankovic, beat American CoCo Vandeweghe 6-3, 6-4; former French and U.S. Open champion Svetlana Kuznetsova defeated Australian Tammi Patterson 6-2, 6-0; and Caroline Garcia, who represented France at the Hopman Cup last week, beat countrywoman Kristina Mladenovic 7-6 (4), 6-4.
Bernard Tomic is the top-seeded man at Sydney, while Halep is the top-seeded woman.
Halep, who has a first-round bye, said Sunday she'll likely carry the injury into the Australian Open, which begins Jan. 18.
"It's difficult to know that you will be injured when you come to Australia. To me it happened this year," she said. "I was not happy but we have to accept it."
At the Hobart International, another of the Australian Open warm-up tournaments, second-seeded Camila Giorgi of Italy beat Zarina Diyas of Kazakhstan 6-4, 1-6, 6-1 and seventh-seeded Alize Cornet of France defeated Denisa Allertova of Czech Republic 6-4, 7-5 on Sunday.
Sloane Stephens, who won the ASB Classic in Auckland on Saturday, was a late withdrawal from Hobart due to a virus.
Former No. 5 Eugenie Bouchard, who is entered at Hobart, says she has "zero expectations" at the Australian Open as she makes her comeback from a concussion she sustained at the U.S. Open when she slipped and fell in the dressing room.
The Canadian made the quarterfinals at last week's Shenzhen Open after a four-month layoff.
"A month or two ago I wasn't even sure I could play the Australian Open, so I'm just so happy to be in Australia, looking forward to playing these two tournaments (with) zero expectations," the 21-year-old Bouchard said Sunday.
She was pleased with her play in China despite losing in the last eight to Hungarian Timea Babos.
"To step on the court and play a full match with no pain, play three matches three days in a row, was a success for me even though I lost the last match," she said.
Bouchard will play American veteran Bethanie Mattek-Sands in the first round in Hobart.