Group One winners Contributer and Complacent have been retired with both suffering minor tendon injuries.
Godolphin made the announcement on Saturday, saying both would go to stud.
Formerly raced in England, Contributer claimed the Chipping Norton Stakes a year ago before going on to win the Ranvet Stakes, earning the title of last season’s champion middle distance horse.
“He was the weight-for-age champion of Australia who possessed an amazing turn of foot and a lovely demeanour,” trainer John O’Shea said.
“His loss is a great blow for the stable. He will be a very hard horse to replace.”
Complacent won the 2013 Spring Champion Stakes for trainer Peter Snowden before running second in the Victoria Derby.
His career was restricted to 11 starts because of injury but he made a triumphant comeback for O’Shea, winning the Group Two Chelmsford Stakes and Group Three Craven Plate last spring.
“He was also a magnificent specimen and a real character around the stable who will be missed by the whole team,” O’Shea said.