Gai Waterhouse's prospects of a seventh Golden Slipper have spiralled dramatically upwards with the win of Santos at Randwick.

The colt firmed from $51 to $11 in markets for the Golden Slipper on March 24 with his dominant victory in Saturday's Pierro Plate (1100m), a race named for Waterhouse's fifth Slipper winner in 2012.

And Waterhouse, who now trains in partnership with Adrian Bott, was quick to compare Santos favourably with Pierro and 2015 Slipper winner Vancouver.

"He is very loose and very fluid. That's what I look for," Waterhouse said.

"Vancouver had it. Pierro had it. That sexy factor.

"He has been our Slipper horse from day one but was immature in the spring so we gave him time."

With Tim Clark aboard, Santos ($6) stalked the $2.70 favourite Legend Of Condor and had the drop on him in the straight.

He went past his rival with ease and raced to away as the favourite struggled.

Exceltic ($8) made some ground but was 2-1/2 lengths from the winner, holding third placegetter Irish bet($7) by a short head.

Santos had two starts in the spring for a third in the Breeders' Plate won by Performer and a fourth behind Legend Of Condor.

"This was a very, very crucial race for us," Waterhouse said.

"All the field are Golden Slipper horses."

Waterhouse said Santos would have one more run before the Slipper but she was unsure where or when while Exceltic's trainer Gary Portelli said the Black Opal Stakes was the likely next option for the colt.

"He still has improvement," Portelli said.

"If he had won we probably would have gone to the Todman Stakes but I think the Black Opal might be the better race for him."