Calyx has been ruled out of the Qicpo 2000 Guineas at Newmarket next weekend.
The news of his defection came just hours after the Kingman colt had pleased connections in a racecourse gallop on Friday morning.
John Gosden's charge looked every inch a future superstar when winning the Coventry Stakes at Royal Ascot last June, but missed the rest of the season through injury.
A tilt at the first colts' Classic of the season had remained under consideration - and there was no immediate change after he eased ahead of stablemate First Eleven in the hands of Frankie Dettori at the end of a workout on the Rowley Mile.
Gosden and Grimthorpe were both suitably impressed, with Gosden saying: "I'm happy with his work - and he had a nice, normal blow.
"He picked up well, and a decision will be made over the weekend. There is no decision now."
However, Teddy Grimthorpe, racing manager to owner Khalid Abdullah, later issued a statement announcing Calyx will not run in the Guineas on Saturday week.
He will instead make his seasonal reappearance in the Merriebelle Stable Commonwealth Cup Trial - better known as the Pavilion Stakes - at Ascot on Wednesday.
The statement read: "Calyx worked on the Rowley Mile course this morning under Frankie Dettori.
"Both John Gosden and Frankie felt that to go straight to the 2000 Guineas after such a long layoff would be asking too much at this stage.
"Therefore he will not run at Newmarket on Saturday week. He is now likely to run in the Pavilion Stakes at Ascot next Wednesday.
"Thereafter, the top mile races will be considered."
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