Sydney, Australia (SportsNetwork.com) - Top seed Simona Halep pulled out of the tournament, while Petra Kvitova advanced and Agnieszka Radwanska lost Tuesday at the Sydney International tennis event, a final hardcourt Australian Open tune-up.
The French Open runner-up Halep, fresh off her title in Shenzhen, China, last week, cited gastroenteritis as the reason for her withdrawal. She believes she contracted the illness while in China and hopes to fully recover in time for the Australian Open, which begins Monday in Melbourne.
"During the tournament in China I got this problem in my stomach," explained Halep. "I was waiting until today to see if I was ready to play again, but I feel like I cannot play. It's tough to play a tournament like this, so unfortunately I decided to withdraw."
Fourth-seeded U.S. Open runner-up Caroline Wozniacki withdrew from this tournament Monday with a wrist injury.
American Nicole Gibbs replaced Halep in the draw and was promptly double- bageled in 38 minutes by rising Czech Karolina Pliskova 6-0, 6-0 on a rainy day in Sydney.
Meanwhile, the second-seeded Wimbledon champion Kvitova defeated Chinese Peng Shuai 6-1, 7-5, while rising Spaniard Garbine Muguruza ousted the third-seeded former Wimbledon runner-up Radwanska 3-6, 7-6 (7-4), 6-2.
In other second-round play involving seeds, No. 5 Angelique Kerber, a runner- up here a year ago, outlasted Russian wild card Daria Gavrilova 6-7 (6-8), 7-6 (7-2), 6-3, Spain's Carla Suarez Navarro upended No. 6 Russian Ekaterina Makarova 4-6, 6-1, 6-4 and wild card and Aussie favorite Jarmila Gajdosova knocked out seventh-seeded Aussie Open runner-up Dominika Cibulkova 1-6, 6-3, 6-4. Cibulkova was a finalist in Sydney two years ago.
Also on Day 3, American Madison Keys beat qualifier and defending Sydney champion Tsvetana Pironkova of Bulgaria 6-4, 1-4, retired and Czech Barbora Zahlavova Strycova dismissed Aussie favorite, former U.S. Open champ and 2005 Sydney runner-up Samantha Stosur 7-6 (7-1), 6-2. Pironkova upset Kerber in last year's final here.
Wednesday's quarterfinals will pit Kvitova against Gajdosova; Kerber versus Muguruza; Keys against Zahlavova Strycova; and Pliskova versus Suarez Navarro.
This week's winner will take home $124,000.