Brenton Avdulla's Sydney premiership chances have been dealt a blow with three of the jockey's rides scratched from Canterbury.

Avdulla trails Hugh Bowman by half a win in his bid for a first title with the latter retaining a full book on Wednesday.

After Canterbury, there is just one metropolitan meeting left for the season.

In Melbourne, Craig Williams leads apprentice Beau Mertens by two winners heading into Wednesday's Sandown program.

Mertens has five rides at Sandown while Williams has eight.