Rayif has been ruled out of the clash of the Guineas winners in the June 16 St James's Palace Stakes (G1) and was the major absentee among the day one declarations for Royal Ascot.
The Aga Khan Studs' homebred defeated Puerto Rico in last month's French version of the Two Thousand Guineas (Poule d'Essai des Poulains (G1)), and was generally an 8-1 shot to come out on top against Bow Echo and Gstaad.
Nemone Routh, racing manager to the Aga Khan Studs in France, said: "It's nothing serious, but he didn't really eat much overnight and he's got a mild fever this morning. We didn't feel like we could put him on a trip over to Britain this evening, so we took the view that we wouldn't declare him.
"We don't think it's anything serious, but it's just fallen at the wrong time. He's been in great form, and he worked brilliantly."
Alongside his half sister Rayevka, who heads to the King Charles III Stakes (G1), Rayif had been set to represent Francis Graffard on day one of a meeting where France's champion trainer expects to saddle a double-figure number of runners for the first time.
The son of Sea The Moon burst onto the scene as a 2-year-old, handing a 2 1/2-length defeat to the Joseph O'Brien-trained Andab in the Prix Francois Boutin (G3) at Deauville in August before rounding off his juvenile season when third to Puerto Rico in the Prix Jean-Luc Lagardere (G1).
