Viddora has pulled up lame from trackwork in Hong Kong with the mare to be monitored ahead of the Chairman's Sprint Prize at Sha Tin.
She worked on the all-weather track on Wednesday morning with regular jockey Joe Bowditch aboard but Hong Kong Jockey Club vet, Dr Peter Curl, later noted she was lame in her right hind leg.
He said she would be closely monitored ahead of Sunday's race.
Viddora ran fourth in last month's Al Quoz Sprint in Dubai before travelling to Hong Kong.
Last-start TJ Smith Stakes winner Santa Ana Lane arrived in Hong Kong for the Chairman's Sprint Prize on Tuesday.
He completed a lap of the all-weather course under track rider Will Stewart on Wednesday as did New Zealander Enzo's Lad.