As impressive as Royal Descent was winning Saturday's Adrian Knox Stakes, it may take more than that to convince owner Gerry Harvey to start her in the Australian Oaks.

The Chris Waller-trained filly raced midfield with cover as Nash Rawiller made sure she conserved her energy over the 2000 metres under her topweight of 59kg.

Royal Descent ($5.50) burst out of the pack and strode to the line 2-1/2 lengths ahead of Express Power ($18) with favourite Unimpeachable ($4.20) another three-quarters of a length third.

"I'll speak to the boss but the Oaks is not a certainty," Waller said.

"If she doesn't go there we know we have a nice filly for the future.

"The way she won under the big weight was impressive."

Rawiller said Royal Descent felt strong at the end of the race and gave every sign she could back up in next week's Australian Oaks (2400m).

"She gave me no indication whatever that she might be training off," he said.

"But she will give Chris an indication whether that has happened over the next few days."

Trainer Kris Lees was also uncertain whether the runner-up would be an Oaks contender while fellow trainer Joe Pride said Unimpeachable's campaign was over.

"That's enough for her," he said. "She's run all her races for this campaign."

Royal Descent is on the third line of betting for the Oaks with the three main contenders - New Zealand Derby winner Habibi, VRC Oaks winner Dear Demi and Longport - all staying in their boxes on Saturday.