Melbourne Victory coach Kevin Muscat says the club is concerned for the health of captain Carl Valeri after revealing that the midfielder's immediate playing future is in doubt due to a condition affecting his balance.

Valeri, 31, missed last week's loss to Wellington Phoenix in Auckland, and won't be a part of the Victory side that takes on Western Sydney Wanderers in a top of the table clash on Saturday night in Parramatta.

Muscat explained that Valeri would undergo tests early next week as he and the club sought to identify the nature of the issue. The championship-winning coach could not yet pinpoint a possible return date for Valeri. "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 at Gosch's Paddock on Friday, with the club unable to have usual access to their home base at AAMI Park due to a series of Taylor Swift concerts being held this weekend.

Muscat refused to speculate on Valeri's affliction. "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.