Aidan O'Brien's 2000 Guineas runner-up Wichita has died after suffering complications in his recovery from a gallops injury in Australia.
Wichita, second to Kameko at Newmarket this summer and a winner of the Group Two Park Stakes at Doncaster on his final racecourse appearance, was in Australia preparing for the Crystal Mile and Cantala Stakes when he was initially injured.
It had been hoped that the three-year-old would make a full recovery from a fracture in his offside hind leg.
But a statement from Racing Victoria on Monday reported that a subsequent injury had befallen Wichita.
It read: "The connections of the Aidan O'Brien-trained Wichita have advised Racing Victoria (RV) that the horse sustained a further injury to its right hind leg while rehabilitating at Macedon Lodge from recent surgery.
"Acting on the advice of stable veterinarians, the connections advise that Wichita was humanely euthanised on Friday 23 October as a result of the complications encountered in its recovery.
"RV extends its condolences to the owners of the horse, trainer Aidan O'Brien, his stable staff and all who cared for the horse and are greatly saddened by their loss."
Wichita, a son of No Nay Never, won three of his nine races - including last year's Group Three Tattersalls Stakes at Newmarket as well as the Park Stakes.
In addition to his neck defeat in the Guineas, he also finished third in two further Group Ones - last year's Dewhurst Stakes and the St James's Palace at Royal Ascot this summer.