David Payne believes Kementari is the only horse who can beat Winx when she returns at Randwick and will be more than happy if Ace High can finish within three or four lengths of the winner.

Ace High is the leading home-grown hope in markets on the Caulfield and Melbourne Cups and begins his preparation in Saturday's Group One Winx Stakes (1400m).

Champion Winx is the short-priced favourite with Kementari the only other runner under double figures and Payne has dared to voice his belief the Godolphin horse can cause an upset.

"Kementari has already had a run and the rest are stayers coming back so he is the only one who can beat her," Payne said.

"He is a good horse in his own right and he was unlucky in the Missile Stakes when he ran second.

"Ace High is not going to show up until he gets up in distance and I just want to see him within three or four lengths.

"If he can finish closer then I'll be rapt but he is being trained for the Melbourne Cup over 3200 metres so I don't expect too much although his trials have been pleasing."

The winner of the Spring Champion Stakes and Victoria Derby last year, Ace High was nosed out of the Australian Derby in the autumn by Levendi.

"He is stronger than he was at three and is a very tough and sound horse with a long preparation ahead of him," Payne said.

The plan is for Ace High to go to the Caulfield Cup at the sixth start of his preparation, stepping up in distance each time.

While Payne thinks Kementari has a chance to topple the champion, both her trainer Chris Waller and jockey Hugh Bowman believe she is in better form than ever as she bids to set an Australian record 26 consecutive wins.

"She knows when it's game day," Bowman said.

Payne will also test the credentials of three-year-old Momentum Factor in Saturday's Group Three Up And Coming Stakes (1300m).

The gelding, a Warwick Farm maiden winner over 1100m, is by dual Group One-winning sprinter The Factor out of Angel's Breath who won up to 1400m.

"I'm not sure where he sits so we thought we would give him a test at this level in an early season race," Payne said.

"He can always come back in distance and grade if it doesn't work out."