The Tony Cruz-trained California Voce has been withdrawn from next weekend’s BMW Hong Kong Derby (2,000m), while hot early favourite Helios Express is being monitored after missing two days of work.

Also withdrawn from the second leg of the four-year-old series, the Classic Cup (1,800m), earlier this month because of a lame left fore, last-start winner California Voce was again found to be lame in his left fore after a barrier trial on Thursday this week.

The scratching of California Voce opens the door for first reserve Elliptical to take his place in the race for trainer Caspar Fownes.

As short as $2 in overseas fixed-odds markets after sweeping to victory in the Classic Mile and Classic Cup, Helios Express remains on track for his bid at a Classic Series clean sweep despite suffering an infection this week.

While Helios Express was “found to have a mild infection in the right fore foot associated with a previous hoof wall quarter crack”, the son of Toronado “is currently under veterinary and farrier management and was examined by the Department of Veterinary Regulation, Welfare & Biosecurity Policy [on Friday morning] and reported to be sound and able to return to normal training with continued monitoring”.

Twelve-time champion trainer John Size, who is bidding to win his fourth Derby, confirmed Helios Express “has responded well to veterinary and farrier treatment and will continue to be aimed at running in the Derby” after missing work on Tuesday and Wednesday.

California Voce was considered a $26 fixed-odds chance in the Derby, while Ensued ($6.5), Galaxy Patch ($7), Massive Sovereign ($8) and Star Mac ($9) are the others in single figures.

Meanwhile, Hugh Bowman, who has been aboard for Helios Express’ past three victories, will travel to Sydney to ride on Golden Slipper Day at Rosehill the day before partnering Helios Express in the Derby.