Melbourne Victory captain Carl Valeri has been diagnosed with an inflammatory condition affecting part of his brain.
Valeri has been sidelined since his last appearance for the club against Adelaide United on November 28.
While the full results of extensive tests will not be known for at least another fortnight, Valeri has responded well to initial treatment.
"Carl developed a medical condition two weeks ago that affects his balance and coordination. He had a viral upper respiratory tract infection in the week leading up to this," Melbourne Victory club doctor Dr Krishant Naidu said.
"Carl had a progressive loss of balance and coordination and became unable to train.
"He has had specialist reviews with an ear, nose and throat surgeon and a neurologist with extensive investigations.
"To date, these have revealed an inflammatory condition affecting part of his brain.
"The complete results of these tests will not be known for at least a further two weeks.
"These results will likely elucidate the exact nature of this illness.
"Carl has had treatment for the inflammation and has responded with improvement in his balance and coordination.
"Carl will reintegrate into training in a graduated program as he continues to improve."
Melbourne Victory and Carl Valeri would like to thank everyone who has offered their support and well wishes in his absence.