The chances of Nostradamus emulating his brother in the Blue Diamond Stakes will become clearer when he takes on boom colt Rubick in Saturday's Prelude at Caulfield.

Nostradamus is a half-brother to 2010 Blue Diamond winner Star Witness and is among a classy line-up of colts set for a showdown on Saturday in a race which should decide favouritism for the $1 million Blue Diamond on February 22.

Trained by the Hawkes Racing partnership, Nostradamus scored a convincing debut win at Flemington last month and sits on the fourth line of betting for the Blue Diamond.

Among his opposition in the colts and geldings Prelude (1100m) is Blue Diamond favourite Rubick, the Mark Kavanagh-trained Chivalry and Blue Diamond Preview winner Mohave.

"He won well on debut but probably didn't meet a lot of good horses. So Saturday is going to be his test," co-trainer Wayne Hawkes said of Nostradamus.

"Whoever wins on Saturday will have bragging rights and be favourite for the Blue Diamond. So it will be a good race."

Hawkes has seen the wins of Nostradamus' opposition, including Rubick's sparkling debut at Randwick on January 25, and respects the opposition but is happy to be taking them on.

"I wouldn't swap," he said.

Nostradamus, a son of Medaglia D'Oro out of Leone Chiara, will be ridden by Glen Boss.

Hawkes said the colt, a $500,000 yearling purchase, had always shown he could be a Blue Diamond prospect.

"Right from day one he was always top of the pops. He always showed something straight off the bat. Most good horses do," Hawkes said.

But he added the colt had only won a Flemington Saturday race at this stage and still had to prove himself as he stepped up in grade.

Hawkes said the Gerald Ryan-trained Rubick "couldn't have done any more than he has done" but noted he had to travel from Sydney and race the Melbourne way for the first time.