Champion jockey Craig Williams will have free rein aboard second favourite Green Moon to take it up to his Cox Plate rivals, particularly the "suspect" trio of three year-olds who hold the key to the race.

Owner Lloyd Williams said his usual meticulous planning will conclude on race morning and he will leave the race tactics to his rider.

But Williams gave every indication he would be happy to see his namesake attempt to put the pressure on the favourite Pierro and take control of Australia's most prestigious race.

"If Craig wants to take it up a half mile from home and turn it into a race, that's fine," Williams said.

"Or if he wants to sit and wait, he can do that because this horse can sprint."

The prolific owner who has a big hand in most of Melbourne's spring features said he doubted the stamina of the three-year-olds, Pierro, Proisir and All To Hard, saying they will need to be tougher than they've shown so far if they are to beat Green Moon.

"I can tell you one thing, my horse will turn it into a tough race," he said.

"He's ready to run a mile-and-a-half so he'll run this race out."

Pierro was an easing favourite for the $3 million Cox Plate (2040m) on race eve with $4.40 available and with better odds expected on track.

Green Moon held the second line at $5.50 with the New Zealander Ocean Park next at $7.

Williams's views are a powerful addition to those expressed earlier in the week by champion jockey Craig Williams who declared he would go to war on Green Moon.

Another clue to the jockey's opinion of the horse is the belief among Green Moon's connections that he could even reconsider his Melbourne Cup options after the Cox Plate.

Williams is booked for the Cup favourite and reigning titleholder Dunaden on which he won last Saturday's Caulfield Cup.

But when the Melbourne Cup mount on Green Moon was discussed earlier this week, the horse's part-owner Nick Williams suggested the horse's Cox Plate performance might convince Williams to stay on him.

Green Moon, yet another of the internationals who are dominating spring racing in Sydney and Melbourne, has been in the Williams stable for more than 12 months, having done his early racing in England where he won three races.

His last-start win in the Turnbull Stakes (2000m) at Flemington was his third in Australia at his third run this time in - and one which his owner said he is capable of improving on.

That success in the Turnbull, added to Pierro's second placing in the Caulfield Guineas, led to Craig Williams switching from the Waterhouse-trained colt and causing Green Moon's price to tumble.

In a race in which the betting was stifled two weeks ago by Pierro, there are now five runners under double figure odds, including the Waterhouse second-string More Joyous who has been at the centre of high tension since her trainer chose barrier 11 for her.

Theories on the Waterhouse decision to choose the wide barrier, which owner John Singleton labelled as "suicidal", have abounded since Tuesday's draw.

One of them has More Joyous and her stablemates Pierro and Proisir leading the field to the winning post the first time and establishing the pattern of the race.

For the Williamses and Green Moon, it would no doubt be a tactic they approve of.