Serena Williams twisted her left ankle late in her second round match against Serbia's Bojana Jovanovski and needed about 10 minutes of treatment, including having her ankle restrapped, before she went on to secure a 6-2 6-4 victory.
The American had scans on the ankle later on Wednesday, which confirmed she would need to withdraw from the tournament.
"I'm still hopeful of playing the Australian Open," Williams said.
The first grand slam tournament of the season starts on January 16. Read the full story.