Top seed Simona Halep withdrew from the Sydney International tennis tournament on Tuesday with gastroenteritis.

Halep started the 2015 season by winning her ninth career title at the Shenzhen Open. She believes she contracted the illness while in China and hopes to fully recover in time for the Australian Open, which starts next Monday at Melbourne Park.

"I feel like I cannot play," Halep said. "I came here to play all the tournaments so it's not good to stop. I didn't play already for three days. But I have to recover first myself and then think about tennis."

American Nicole Gibbs replaced Halep in the draw and was beaten 6-0, 6-0 by Karolina Pliskova of the Czech Republic in the first round Tuesday.

Fourth-seeded Caroline Wozniacki withdrew from the tournament Monday with a wrist injury.