Melbourne Victory captain Carl Valeri's immediate playing future is under a cloud after coach Kevin Muscat revealed that he is suffering from a condition affecting his balance.

"It's not good news for Carl unfortunately. He was diagnosed with a virus 10 or 12 days ago, that's now developed into some sort of condition that's affected his balance, so he's undergone quite a bit of testing in the last few days, with some more testing early next week," Muscat said.

"And at this point in time it's obviously a matter we're taking very seriously. But I'll have more based on what's uncovered in the testing early next week.

"Our thoughts are with him at the moment because like I said it's something we're taking very very seriously, the wellbeing of one of our players."

Melbourne take on Western Sydney on Saturday night at Pirtek Stadium in a top of the table clash.