Bookmakers are taking no chances with Australian Derby favourite It's A Dundeel but he won't get things his own way.

Markets were suspended on Monday night with the announcement second favourite Fiveandahalfstar was out of Saturday's Derby (2400m) at Randwick due to injury.

Following the declaration of the final field of 10 on Tuesday, It's A Dundeel was in to $1.25 to complete Sydney's three-year-old triple crown.

But connections of the other nine runners say the Murray Baker-trained colt will be made to prove he is a genuine stayer and are optimistic about their charges.

In the absence of the front-running Fiveandahalfstar, the Gai Waterhouse-trained Hippopus will put him to the sword.

"We will be making it a genuine test," Waterhouse's racing manager Bruce Slade said.

"Hippopus is a genuine mile-and-a-half horse and we will definitely be positive from the start.

"We will be out to make it a true run race."

Hippopus, who finished second in Saturday's Tulloch Stakes (2000m), is on the third line of betting at $13 with the winner Philippi second elect at $8.

Kingdoms ($35) finished fourth in the Rosehill Guineas and despite the fact he was almost nine lengths from It's A Dundeel, trainer John O'Shea was talking him up.

"He was ridden upside down in the Rosehill Guineas. He is much better ridden back," O'Shea said.

"I'm disappointed Fiveandahalfstar isn't there. He would have made it a genuine mile-and-a-half race.

"But I know my horse will run a strong 2400 metres."

Sydney-based Bjorn Baker, who is looking after It's A Dundeel until his father Murray arrives from New Zealand on Thursday, admits there could be a query on the distance qualifications of the colt but not his class.

The favourite for the Victoria Derby in the spring, It's A Dundeel finished out of the placings behind Fiveandahalfstar in the Flemington race.

"There is some debate over the distance and whether he is better at a mile to 2000 metres," he said.

"The instructions to James McDonald will be to keep out of trouble. It's all up to him.

"I just think he might win because he is too good."