Gai Waterhouse confirmed the loss of one Golden Slipper horse before producing another one for the $3.5 million race - all in the space of a few hours on Wednesday.

As Waterhouse resigned herself to the likely retirement of unbeaten Fighting Sun, the blow was softened by Wandjina's win in the wet in the Australian Turf Club Handicap at Warwick Farm.

Fighting Sun emerged as Tulloch Lodge's top seed for the Golden Slipper after strolling home in the Canonbury Stakes at Rosehill last Saturday, only to go amiss the next day.

"They are thinking seriously of retiring him," Waterhouse said of Fighting Sun as she waited for Wandjina and Nash Rawiller to return to scale.

While Fighting Sun's autumn defection will hurt, Waterhouse rarely has worry about the depth in her her two-year-old team, especially with owners like Dr Edmund Bateman willing to part with $1 million for horses at the annual round of Australian yearling sales.

That's what Wandjina cost and Waterhouse will back herself to the hilt to ensure this latest winner by in-demand stallion Snitzel turns out to be a solid racing and breeding investment.

"He's coming late in the preparation for the Golden Slipper but he's all brilliance and that's what you need, you need brilliance," Waterhouse said.

Wandjina was first-up having not raced since he was unplaced as favourite in the Breeders' Plate in October but he looked destined for better wins after landing a $1.90 to $1.55 move.

The result was never in doubt as Rawiller drove the colt to a 3-1/4 length victory over the fast-finishing first starter Country Warrior ($7).

Another debutante, the Gerald Ryan-trained Aerobar ($20), was a long neck away third.

As she figures out the best path to the Golden Slipper for Wandjina, Waterhouse has more pressing two-year-old matters with a pair of runners in the Blue Diamond Stakes at Caulfield on Saturday.

She has Nayeli and Francesco engaged as she chases her first win in the $1 million race.

Nayeli is the horse Blue Diamond bookmakers rate as her best chance with the filly sitting on the fourth line of betting at $9.

"She beat the colts at Caulfield and she's gone ahead since then," Waterhouse said.

"She is totally under the radar."