Former world number one Venus Williams has withdrawn from the first Grand Slam of the year - the Australian Open starting next Monday because of an autoimmune disease that causes fatigue and joint pain.
"I regret to announce that I am withdrawing from the 2012 Australian Open. After several months of training and treatment, I am making steady progress to top competitive form. My diet and fitness regimen have allowed me to make great strides in terms of my health and I am very close to being ready to return to WTA competition," said the seven-time Grand Slam title winner, who has been out of action since the US Open in August last year.
She however, expressed her eagerness to return to competitive tennis. "I have every intention to return to the circuit in February," she said.
Meanwhile, sister Serena, whose 13 Grand Slam titles include five at the Australian Open, badly sprained her left ankle at a tournament in Brisbane last week and is unsure if she'll be able to play in the first Grand Slam of the year.
Top seeds toil hard
World number one Caroline Wozniacki and her chief rankings rival Petra Kvitova had demanding three-set introductions to the Sydney International in their first official matches of the season on Tuesday.
After her two hour and 22 minute match against the 18th-ranked Slovakian Dominika Cibulkova, the Danish world number one said her 7-5, 2-6, 6-4 victory had been a tough contest.
Wozniacki set up a quarter-final clash against Polish seventh seed Agnieszka Radwanska, who overcame Germany's Andrea Petkovic in straight sets. Wozniacki leads Radwanska 5-1.
Kvitova also a had tough fight against Romania's Alexandra Dulgheru, needing two hours and 18 minutes to defeat the world number 66.
Defending champion Li Na also had a difficult time before subduing South African Chanelle Scheepers 2-6, 6-4, 6-1 to set up a quarter-final with Lucie Safarova of the Czech Republic.
French Open champion Marion Bartoli skated into the quarters with a 6-0, 6-3 win over Australian Jelena Dokic and will play either third seed Victoria Azarenka or Jelena Jankovic of Serbia in the last eight.