Sizing John has been ruled out for the rest of the season after suffering another injury setback.
Jessica Harrington's charge completed the rare treble of the Irish Gold Cup at Leopardstown, the Cheltenham Gold and the Punchestown Gold Cup in the first half of 2017.
He made a flying start to the following campaign in the John Durkan, but disappointed at Leopardstown over Christmas - and injuries then kept him off the track for more than two years.
The 10-year-old made his long-awaited return over hurdles at Punchestown on New Year's Eve - and while he fell three flights from the finish, connections took enough encouragement from his performance to aim for a second win in this weekend's Paddy Power Irish Gold Cup.
However, he will not be lining up at the Dublin Racing Festival and has also been scratched from the Cheltenham Gold Cup, next month's Betfair Ascot Chase and the Randox Health Grand National in April.
Harrington posted on Twitter: "Sadly Sizing John will not be running in the Irish Gold Cup at Leopardstown.
"He was not 100 per cent this morning following his last fast work at the Curragh yesterday. This is a new injury, and it will rule him out for the rest of the season. (It is) very frustrating for all our team."
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