Doubles specialist Casey Dellacqua has been forced to withdraw from the Australian Open due to the lingering effects of a concussion she sustained at the China Open in October. (All the latest Tennis Updates)
The 30-year-old Australian, who reached two doubles Grand Slam finals this year, fell heavily during the Beijing tournament and was hospitalised.
Her manager, Sam Maxwell, said on Friday that Dellacqua has been diagnosed with post-concussion syndrome, putting her playing future in doubt.
Maxwell said Dellacqua was still having headaches, neck pain and is "still not in a position where she is able to train to the level required to be able to play professional tennis".
She will also miss the Hopman Cup mixed-teams event in Perth - where she was scheduled to partner Lleyton Hewitt - and the Sydney International.