Trainer David Vandyke is as bullish as ever about his two-time Group 1 winner Yankee Rose's bid to win the William Hill Cox Plate.

Pundits and bookmakers, alike, have pegged the 2040m weight-for-age feature at Moonee Valley as a two-horse race between Winx and Hartnell, but Vandyke said his filly will stand up to be counted.

"Winx is a champ, and our filly is not at this stage - and we've all seen what Hartnell's done in Melbourne," Vandyke told Racing.com's Racing Ahead on RSN 927.

"But they're going to have to bring their A-game, because if there's a chink in either of those two horses' armour on race day, our filly will find it out because she's in devastating form."

Vandyke backed up Yankee Rose from her Flight Stakes runner-up showing behind subsequent Thousand Guineas winner Global Glamour, to success in Saturday's Spring Champion Stakes (2000m) at Randwick.

Her second Group 1 success marked Victorian provincial star jockey Dean Yendall's first win at the highest level.

When Vandyke first flagged his wish for Yankee Rose to run in the Cox Plate back in early June, he didn't have a jockey in mind.

Now, natural lightweight Yendall is locked on board for the $3million feature, with Saturday's ride the perfect prelude for both the jockey and the horse.

"It was as much of a thrill watching Dean after the race as anything," Vandyke said.

"I didn't realise he'd never ridden at Randwick before, and when I booked him, I didn't know he'd never ridden a stakes winner in Sydney.

"He was so calm and confident before the race - full credit to him.

"Even mid-race, when he let the leading division get 3-4 lengths away from him, he was just concentrating on the filly, her rhythm, her breathing... it showed me he's a top-class rider."

And Vandyke pointed out the weight relief in the Cox Plate - she is allocated 47.5kg - will be handy, with Yankee Rose only tipping the scales at 460kg, even after some recent weight gain.

"For her to put on 5kg from the Flight Stakes to the Spring Champion Stakes, it was quite amazing," he added.

"She was such a happy horse at the races on Saturday, too - sometimes when you back horses up, you don't know until they get off the float whether they are going to handle it or not.

"Some horses will sweat up and get quite stressed, but she was beautiful."