Craig Williams has failed in his appeal against a careless riding suspension and will miss the Sydney Cup ride on Big Duke.

Craig Williams will miss the Sydney Cup ride on favourite Big Duke after failing to get a careless riding ban reduced on appeal.

Williams needed to get two meetings shaved off his eight meeting ban from Sandown on Monday to be free to ride the Darren Weir-trained Big Duke in Saturday's $2 million race at Randwick.

Singapore-based Australian rider Glen Boss has picked up the ride on Big Duke after the Racing Appeals and Disciplinary Board dismissed Williams appeal against the severity of the ban at a hearing on Wednesday.