Champion jockey Craig Williams has turned down Gai Waterhouse's invitation to ride star three-year-old Pierro at Saturday week's Cox Plate and will remain aboard Green Moon.
In the wake of a steward's investigation into allegations dumped jockey Damien Oliver bet $10,000 on a rival horse he was racing against in 2010, Waterhouse is now without a jockey for her Cox Plate favourite.
Oliver had been originally penned to mount Green Moon and Williams Pierro, but the jockey was stripped of the ride along with his Caulfield Cup entrant My Quest For Peace as a result of the investigation.
Following colt Pierro's shock defeat in Saturday's Caulfield Guineas, Williams took the opportunity to reunite with Green Moon, a horse he has ridden in its last four starts.
"Gai Waterhouse gave me the opportunity to ride Pierro if I wanted to and I had to weigh up a couple of options which one of them of course was the weight," Williams told media after doing track work with French star Dunaden in Werribee.
"I've had a great association with Green Moon, I've been with him in all his preparation and I'm very excited to be with him in the Cox Plate.
"I'll know if I'm a good judge in a couple of weeks, it looks a very open Cox Plate this year, barrier draws are going to play a major part in it."
Williams has enjoyed two victories on Green Moon, last start in the Group 1 Turnbull Stakes (2000m) at Flemington on October 6 and earlier in the year in the 1600m Group 2 Blamey Stakes on the same track.
A sticking point for Williams' ride on Pierro, and potential other candidates, is the 49.5kg weight allotted to three-year-old colts.
Dwayne Dunn officially ruled himself out of making the weight, prolonging Waterhouse's search for the right jockey.
Williams will attempt to go back-to-back in the 2040m, $3 million classic having ridden the late Pinker Pinker to victory in 2011.
As a result of last Saturday's loss, Pierro has drifted from a $1.85 favourite to $3.95 while Green Moon is in to $5.70.