Two international raiders from the powerhouse stable of Aidan O'Brien are in doubt for the Cox Plate after failing their initial fitness tests.

Champion trainer Aidan O'Brien faces an anxious wait after his two Cox Plate horses, Magic Wand and Armory, showed signs of lameness just two days out from the race.

All 14 Cox Plate runners were inspected by Racing Victoria veterinarians on Thursday and passed fit to start with the exception of the O'Brien pair.

"Magic Wand presented with lameness in her right fore limb, while Armory presented with a degree of lameness in his left fore limb," RV said in a statement.

Both horses will undergo further examinations on Friday when they will be assessed by a panel of three vets, two from RV and one independent.

O'Brien is chasing his second Cox Plate after winning it for the first time with Adelaide six years ago.

Armory is high in Cox Plate betting as a $6 chance while Magic Wand is at $26.