The former world number one Serena Williams suffered another injury scare less than two weeks ahead of the Australian Open with the American forced out of the Brisbane Tennis International with a badly twisted ankle.
There was also bad news for home favourite and top seed Samantha Stosur, who was bundled out early for the second successive year.
Men's top seed Andy Murray was in danger of joining Stosur in an early exit when he dropped the first set against Luxembourg's Gilles Muller before he fought back through a second set tiebreak then blitzed the decider to run out a 4-6 7-6 6-0 winner in just over two hours.
The 24-year-old world number four, who also struggled in the first round on Tuesday before he beat the unheralded Mikhail Kukushkin in three sets, now meets Marcos Baghdatis in the quarter-finals.
Williams twisted her left ankle late in her second round match against Serbia's Bojana Jovanovski and needed about 10 minutes of treatment, including restrapping her ankle, before she went on to secure a 6-2 6-4 victory.
The American had scans later which confirmed she would need to withdraw from the tournament.
She had been due to meet Slovakia's Daniela Hantuchova in the quarter-finals and the injury will now create some doubt as to whether the 30-year-old will be in top form as she attempts to win her sixth Australian Open title at Melbourne Park.