Australian Derby hopeful Ruling Dynasty is suffering from a foot abscess four days out from the Classic at Randwick.
Trained by Bart and James Cummings, Ruling Dynasty is an $11 chance in Saturday's Derby.
James Cummings told stewards on Tuesday afternoon a poultice had been applied to the gelding's off-fore hoof and he would be monitored by the stable over the next few days.
He will also be inspected by the Racing NSW vet before he starts in the Derby.