Zaaki, a firm favourite to win the WS Cox Plate, has been withdrawn from the $5 million race.
Trainer Annabel Neasham made the gut-wrenching decision to scratch the UK import moments before Saturday's deadline.
"It's gutting to be honest. Really frustrating. We take temperatures every morning and he's never had an elevated temperature," Neasham told SEN.
"These things happen and it's just unfortunate timing.
"I just can't believe it but I've got to be grateful I've got another horse who has got a live chance in the field."
Neasham is left with Mo'unga as her runner in the prestigious weight-for-age contest over 2040m at Moonee Valley.
Mo'unga was a clear second seed for the trainer but is now on the fourth line of betting.
Neasham said all was not lost fo Zaaki's spring and there is a chance her stable star could race during the four-day Melbourne Cup carnival at Flemington.
"Hopefully we can get Zaaki right as quickly as we can. He'll be back to fight another day," she said.
Zaaki surged to the top of Cox Plate betting after a string of wins during the Queensland winter carnival.
He had held his place as the horse to beat despite a shock defeat at Caulfield two weeks ago.
Anamoe, Australia's best three-year-old, has taken Zaaki's spot as favourite ahead of the Chris Waller-trainer Verry Elleegant.
Trained by James Cummings, Anamoe will be attempting to complete the Caulfield Guineas-Cox Plate double for the Godolphin operation.
The valuable colt is a $2.90 chance with Verry Elleegant at $3.80 and the Irish-trained State Of Rest the third pick at $6.50 in a reshaped market.
Eight runners will now face the starter after Friday's controversial scratching of Gold Trip.
Australian Associated Press