Blue Diamond Stakes winner Samaready is in doubt for Saturday's McNeil Stakes at Caulfield and her Golden Rose campaign in Sydney is under a cloud.
Trainer Mick Price said the star filly had "gone on strike" on Monday night, refusing to eat her evening meal.
As a result Price was forced to abandon a vital gallop planned for Tuesday morning and will keep Samaready in cotton wool until results of blood tests are known.
While the trainer was philosophical about the setback, he admitted he may have to revise plans for a trip to Sydney for the $1 million Group One Golden Rose.
"I brought her to the track this morning and she seemed bright enough," Price said.
"But I decided not to gallop her just in case."
Price suspects Samaready, who stamped herself as one of the country's best juveniles last season, may have a low-grade infection, although she didn't have a temperature on Tuesday morning.
"We'll have a look at her blood picture and take it from there," he said.
"I can't see it being a massive problem, but I wanted to give her one run before the Golden Rose and it wouldn't be practical to do that a week before the race."
The Group One Golden Rose is run over 1400m at Rosehill on September 15.
Samaready resumed racing last Saturday week at Caulfield, finishing fourth to Elite Elle in the Quezette Stakes.
Price had mapped out a spring program that included the Golden Rose and the Group One Thousand Guineas at Caulfield next month.
Should she miss the Sydney race, it is anticipated Samaready will still be aimed at the Thousand Guineas.