Australian Casey Dellacqua has been ruled out of the Australian summer of tennis due to injury.
Dellacqua will miss her home slam due to the ongoing effects of a concussion she suffered after falling heavily at the China Open in October.
She has since been diagnosed with Post-Concussion Syndrome, also placing doubt on her future as a tennis player.
"Casey is still experiencing 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," manager Sam Maxwell said.
"There is no timeline on Casey's return at present, however we expect her to return to light training in the coming weeks with a return to the tour some time after the Australian summer."
Dellacqua, who was due to line up at the Hopman Cup alongside Lleyton Hewitt in January, will be replaced in the event by Jarmila Gajdosova.