Christian Reith has set the bar high for debut winner Earthquake, comparing the filly to her multiple Group One winning stablemate Guelph.

Both Peter Snowden-trained fillies are by champion Darley stallion Exceed And Excel but Reith, who rode Earthquake to her win at Randwick on Saturday, believes the similarities go further than their sire.

Her win in a four-horse barrier trial last month wasn't enough to convince punters who sent her out at $6 with Headwater Country the $3.50 favourite.

Reith rides a lot of work for Darley and is the go-to man when Kerrin McEvoy is interstate or absent for other reasons.

"She's an absolute star," Reith said.

"She was always going to be and in my opinion she will be the next Guelph."

Reith was content to let Earthquake travel behind Sheer Style ($6.50) in the 2yo Plate Plate (1000m) while the favourite was in the second half of the field.

Earthquake gathered in Sheer Style in the straight and asserted her authority to win by 2-1/2 lengths.

Headwater Country led in another division of the race, 5-3/4 lengths from the runner-up.

"She has got the perfect attitude, perfect nature, and the perfect temperament," Reith said.

"She's been getting better and better each week at home and is only going to improve.

"She's very exciting."

Reith was convinced he had ridden another winner on the Randwick program but Shamus was nosed out of the 3yo and upwards benchmark 85 race when Jim Cassidy arrived late on Field Marshall.

Kathy O'Hara did manage to get a double but had to work harder for her second winner than her first.

Wearing blinkers, the front-running Capital Commander got her own way in front for a decisive win over 1600m to make amends for her last start second, but O'Hara had to take her case to the stewards' room to get the decision on Fulminate in the 1500m benchmark 80.

O'Hara was successful in her objection against apprentice Lester Grace aboard She's A Girl who shifted ground twice inside the final 200 metres.

The margin between the pair was a half neck and stewards agreed with O'Hara her mount would have won if not for being impeded.