Sans Frontieres has suffered a training setback and will not be able to take up his entry in the King Edward VII Stakes at Royal Ascot next week.
Trainer Jeremy Noseda bypassed last weekend's Investec Derby with Robert Ogden's son of Galileo in favour of an outing at the Royal meeting, but all plans for the three-year-old are now on hold.
Ogden's racing manager, Barry Simpson, said: "He has had a training setback and will not run at Ascot.
"It is only minor but will prevent him running at Ascot. We are getting a second opinion midweek though, and we will have a better indication of what to do after that.
"Initial indications are that he would be out for six weeks but we have to think about bringing a horse back for the autumn for just one race when we do look upon this horse as a four-year-old type.
"He is from a maturing family so we will have to discuss the views of the vets with Sir Robert and decide what do to about the rest of this year."
The colt was touted as a Derby prospect after taking third in the Dante Stakes, but connections elected to miss the Classic due to his inexperience.
Simpson added: "We decided the Derby wasn't the right race for him as he was immature, but this happened last week so he wouldn't have been able to run anyway."