Craig Williams' misfortune has led to Dwayne Dunn getting his chance at a first Cox Plate win on Hauraki.

Dunn replaces Williams on the Epsom Handicap winner in Saturday's weight-for-age feature at Moonee Valley after Williams failed to have a careless riding ban overturned.

Williams was suspended at Caulfield last Saturday but took his case to the Racing Appeals and Disciplinary Board on Tuesday hoping to have the 12-meeting ban at least reduced.

Dunn has gone close to winning a Cox Plate when Happy Trails ran a half-head second in 2013 to three-year-old Shamus Award.

The jockey's next best finishes have been a third on Rekindled Interest in 2011 and a fourth on Zarita in 2008.

"I've had a second, a third, a fourth. It's been a race that's been good to me but it's still a bit of a thorn in my side. It would be nice to get one," Dunn said.

While defending champion Winx and Hartnell dominate the market and the discussion on Saturday's race, Dunn is hoping Hauraki might be able to cause a boilover.

Hauraki, a stablemate of Hartnell, was second to Winx in the George Main Stakes two starts ago before flashing home late to win the Epsom Handicap with James McDonald aboard.

McDonald rides Hartnell in the Cox Plate with the Turnbull Stakes winner at $3.20 behind Winx at $1.85, while Hauraki is at $19.

"I think he's a great chance," Dunn said.

"He got beaten a length and a quarter behind Winx. His Sydney form has been outstanding.

"It's probably a matter of the two-horse war maybe unfolding in front of me and if there's any chink in their armour, I can chime in," Dunn said.

"My horse is sort of a get-back run-on horse as well. While everyone talks about it as a two-horse race, hopefully they start thinking about themselves and forget about a couple of us that are chances in the race if they have their issues."