While the money men have spent the week haggling over Zoustar's worth at stud, Chris Waller's job has been to make sure the colt is comfortable with the Flemington straight.

Widden Stud has secured the future racing and breeding rights for Zoustar for an estimated $20 million which includes bonuses if he can add Saturday's Group One Coolmore Stud Stakes (1200m) to his Golden Rose victory.

A less-than-impressive jump-out last Friday gave his trainer some concern but a second work-out on Tuesday restored Waller's confidence.

"The straight course is always a problem for any horse going there for the first time," Waller said.

"I'm grateful for the opportunity to be able to give him another run on the course this week.

"He galloped with Moriarty who is a genuine weight-for-age performer and for a three-year-old to beat a horse like that, it's an important thing."

Zoustar is the odds-on favourite for the Coolmore which Waller sees as a vital test ahead of a possible trip to England next year.

"If he wins it will be a great test for Royal Ascot and the tough straight courses they have over there," he said.

Waller said the stud deal meant Zoustar was now the most valuable horse he had ever trained but there was still more work to be done.

"Part two starts now," he said.

"I had no part in selling him. He sold himself.

"He is a beautiful type and ticks all the boxes."

Zoustar is from the first crop left by 2008 Coolmore winner Northern Meteor who died at Widden in late July from colic.

The colt's Coolmore mission will be entrusted to veteran jockey Jim Cassidy who has been overshadowed by the hype this week.

If Zoustar wins the Coolmore as expected, it will give Cassidy his 100th Group One winner and he will become just the third Australasian jockey to reach the milestone, joining George Moore and Roy Higgins.