Glamour colt Zoustar has turned in a track gallop that has trainer Chris Waller confident a reported $20 million offer will not be enough to buy the colt.

Considered one of Australia's hottest stallion prospects, Zoustar left Waller searching for superlatives after the three-year-old's final serious piece of work heading into the Coolmore Stud Stakes.

It could easily be the gallop that lays the foundation for another $10 million to be added to Zoustar's value should he win Saturday's Group One at Flemington.

"It was close to the best work, if not the best work, I've seen from him," Waller said.

Zoustar was paired with Mackinnon Stakes-bound Moriarty and sat behind him before peeling out at the 400m mark and going on to defeat his older stablemate.

"I think he'll be worth more money on Saturday afternoon," Waller said.

Zoustar emerged as a much sought-after colt in the wake of his sire Northern Meteor's sudden death in July.

Northern Meteor was crowned champion first-season sire for 2012-2013 and his demise put the spotlight on his best sons.

Zoustar confirmed that early interest in his career beyond the racetrack wasn't misplaced when he claimed the Group One Golden Rose last month.

But Waller thinks Zoustar can reach even greater heights and hopes he can train him at Royal Ascot next year, even if a stud deal is done.

"He could be the next big thing," Waller said.

"He's still got a long way to go but it's just exciting to have a horse doing what he's doing this early in his preparation.

"I've been fortunate enough to have quite a few good horses but we see that usually in the twilight of their career or certainly in their mature years. But for him doing it at this early stage is really exciting.

"I'd love to get the chance to train him at Ascot. I think he would be the perfect horse for it."

Zoustar will give jockey Jim Cassidy a golden opportunity to bring up his 100th Group One win victory.

Cassidy brought up his 99th Group One success on Zoustar in the Golden Rose but his latest attempt to reach the milestone on Hawkspur in the Caulfield Cup came unstuck.