Telescope has a sore left shin and "won't be running" in the Investec Derby at Epsom on 1 June, said trainer Michael Stoute.
The Galileo colt had a racecourse gallop at Lingfield on Wednesday, in which he was described as only "workmanlike" by the Newmarket handler.
He has since developed a sore shin, with Stoute of the opinion the premier Classic will now come too soon.
Stoute said: "He has had hold-ups here and there and hasn't been giving us the right signs."
Asked if he was definitely out of the Derby, Stoute added: "He's not going to run."
Telescope missed an intend prep run in the Dante Stakes at York last week after grazes he sustained on his legs became infected.
He has not raced since winning a strong Newmarket maiden last September.
Amongst Telescope's owners is former Manchester United manager Alex Ferguson.