Star colt Pierro has been retired with stud negotiations to begin in earnest over the next few weeks.

His retirement following his second to Sacred Falls in Saturday's Doncaster Mile comes just days after that of champion Black Caviar with whom Pierro's name has been mentioned as a possible mate in the spring.

Although this was expected to be his last racing season, Pierro's retirement on Sunday robs the Sydney autumn carnival of a showdown between him and three-year-old triple crown winner It's A Dundeel in next week's Queen Elizabeth Stakes at Randwick.

Owners Greg and Donna Kolivos have fielded interest from studs since Pierro completed the two-year-old triple crown a year ago but have held off while they enjoyed his racing career.

"We could have sold him ten times over in the past year," Greg Kolivos said.

Labelled the best horse in her stable ever by Gai Waterhouse, Pierro retires with 11 wins from 14 starts. He suffered his first defeat in last year's Caulfield Guineas when beaten by Black Caviar's half brother All Too Hard who is headed to Vinery Stud in the spring.

Pierro then ran third behind Ocean Park and All Too Hard in the Cox Plate.

After returning from a summer break, Pierro won the Hobartville Stakes before again stepping out of his own age group to record Group One weight-for-age wins in the Canterbury Classic and the George Ryder Stakes.

His regular partner Nash Rawiller said after the Doncaster he hoped Pierro would run in the Queen Elizabeth.

"I've never had a horse going so good that's been beaten," Rawiller said.

"I want to see him in the Queen Elizabeth. I'd like to see him go out on a winning note."

Unfortunately for the jockey, that was not to be and he voiced his disappointment on Twitter.

"Terribly sad news that Pierro has been officially retired, one horse that could never be replaced at Tulloch lodge!," he said.

A son of champion racehorse Lonhro, Pierro was sold as a weanling as part of a draft from Darley.

Kolivos paid $230,000 for the colt as a yearling and he leaves the track with earnings of more than 4.5 million.