Darley knows how to set a horse for one the hardest doubles in Australian racing.

But that doesn't make it any easier with Blue Diamond Stakes winner Earthquake going into the Golden Slipper at Rosehill on Saturday.

Sepoy carried Sheikh Mohammed bin Rashid Al Maktoum's Darley colours to win both races and Earthquake is a pronounced favourite to follow in his hoofsteps.

If having the record books stacked against her isn't enough, Earthquake will have to overcome a minor health scare.

She was placed on antibiotics because of a temperature spike on Sunday but proved her fitness with a Warwick Farm gallop on Wednesday.

"Not many horses have done the Blue Diamond and Golden Slipper double and perhaps the temperature at the weekend is an indication of just how hard it is to do," Darley bloodstock manager Jason Walsh said.

"I know Peter has been very open about two weeks being a long time for a two-year-old and unfortunately we got that message loud and clear this week."

John's Hope (1972), Manikato (1978), Bounding Away (1986) and Courtza (1989) won both races before Sepoy's double in 2011.

Walsh, an integral part of Darley's day-to-day operation, said Earthquake's speedy recovery was a bonus.

"I'm pleased to say that she's surprised us with how well she has rebounded," he said.

"She worked yesterday (Wednesday) and for all intents and purposes she has worked as normal and as well as she ever has."