This season's three-year-old colts have been hailed as the best for years but for two of the stars, it seems Sydney's autumn carnival will be their swan song.

Pierro and All Too Hard are destined for stud careers in the spring with It's A Dundeel the only one of the big three slated to race on.

All Too Hard's value as a stallion has been determined at around $20 million following his acquisition by Vinery Stud while Pierro's owner Greg Kolivos is considering offers.

A half-brother to Black Caviar, All Too Hard will run in the All Aged Stakes on Saturday week before a decision is made on a trip to England.

Pierro is the favourite for Saturday's Doncaster Mile and a win could mean a clash with It's A Dundeel in the Queen Elizabeth Stakes a week later, or the Doncaster could be his last race.

"There has been interest in him from studs since he was a two-year-old," Kolivos said.

"I don't know whether a Doncaster win makes him more valuable.

"I'll find out in time. The pure monetary aspect isn't the critical thing.

"If it was we would have sold him ten times over in the last year. That's not to say we're ignorant of how valuable he is."

A son of Lonhro who stands at Darley, Pierro was among a group of weanlings moved on by the stud and eventually made his way to the Magic Millions yearling sale where Kolivos and his wife Donna paid $230,000 for him.

He racked up the two-year-old triple crown and continued his winning ways until his ninth start when his colours were lowered by All Too Hard in the Caulfield Guineas.

He suffered his second defeat in the Cox Plate when third behind Ocean Park and All Too Hard but those are only two occasions he has been beaten.

His trainer Gai Waterhouse mapped out an autumn campaign which has included one start against his own age in the Hobartville Stakes and two at weight-for-age in the Canterbury Stakes and the George Ryder.

Kolivos admits he's not a breeding expert but says he has had plenty of advice from those who are.

"We're racing enthusiasts and not into breeding so much," he said.

"But we would retain an interest when he goes to stud. We would find it difficult not to."

Pierro is the second foal of imported mare Miss Right Note who has also produced a yearling full-sister to the superstar.