Cavalryman has suffered a last-minute setback ahead of Tuesday's Emirates Melbourne Cup.
The Godolphin runner is reported to have a fetlock issue with trainer Saeed bin Suroor's team having taken X-rays of the problem.
Those scans will now be assessed and if Cavalryman remains in the Flemington feature, local officials will check on his fitness before allowing him to start in the two-mile event.
The Racing Victoria stewards tweeted: "Swelling near fore fetlock. Stable have taken X-rays. To be vetted on arrival if remains in."
If Cavalryman does make the line up, he will be having his second crack at the race having finished 12th back in 2012.
Meanwhile, rank outsider Sea Moon was withdrawn from the race that stops a nation because of a high temperature, leaving the 154th version of the US$5.5m race with only 23 runners.
