Craig Williams' chance to join an elite group of grand slam winning jockeys is in doubt with an injury scare for Godolphin's Cavalryman.

Williams needs only the Melbourne Cup to complete the set and join seven other riders to have won the Melbourne Cup, Caulfield Cup, Cox Plate and Golden Slipper.

In 2011, a suspension cost Williams the winning ride on Dunaden in what he describes as the holy grail of world racing.

Cavalryman was found to have swelling in a fetlock which surfaced on Monday afternoon.

X-rays of the injury will be sent to Godolphin's leading vets.

Stewards will inspect the horse at Flemington on Tuesday if Godolphin decides to run him.

Williams may have more reason for regret after admitting he was offered the ride on Admire Rakti earlier this year.