Derby hero Masar will miss Saturday’s Coral-Eclipse at Sandown due to a late setback.
Charlie Appleby’s charge was set to try to supplement his Epsom victory in the 10-furlong feature, but he was found to be sore following exercise on Friday and all plans are now on hold.
The trainer said: “Unfortunately after exercise this morning, when he was cooling out, he had inflammation and soreness in his right off-fore.
“It was under observation during the course of the day and we felt this afternoon the soreness and the inflammation were still there.
“After speaking to His Highness Sheikh Mohammed, his first concern was to make sure that we were doing what was right for the horse and best for the horse.
“Therefore it was decided not to run him.
“He is under veterinary observation and until the inflammation comes down, we won’t be any wiser as to what extent of an injury we are dealing with. It will be over the course of the next 48 hours.
“First and foremost we need to get the inflammation down – that is what our priority is. It looked like it was a bang, but until the inflammation comes down, you don’t know.
“We’ve got an inflamed right fore that is sore and we need to investigate once we reduce the swelling.”
While Masar misses out, Appleby will still be represented by 2016 race winner Hawkbill, who will now be ridden by William Buick.
“He’s a previous winner of the race and he’s there genuinely on his merits,” said the Newmarket handler.
“He’s in good order and if he’s on his A-game, I think he’ll test the three-year-olds, which is what it’s all about.”
Masar’s absence means the John Gosden-trained Roaring Lion looks likely to sent off favourite for the Group One highlight.
He finished third in the Derby and fifth in the 2000 Guineas behind the reopposing Saxon Warrior.
However, on his only start to date over a mile and a quarter he ran out an impressive winner of the Dante Stakes at York.
Gosden said: “He ran great in the Guineas. I think the Guineas is the best form, so to that extent we’ve got it all to do, but we know a mile and a quarter on top of the ground suits us.”
Saxon Warrior is set to be one of three contenders for Aidan O’Brien and he makes a swift reappearance after finishing third in the Irish Derby last Saturday.
The Ballydoyle handler has reiterated he will be observing Saxon Warrior closely in the lead-up to the race, but is happy to come back in distance with his star.
He said: “Obviously he hasn’t done anything since (Irish Derby) and we’ll watch him closely all the way up to the race, but he seems to have taken it well.
“We won’t really know until we run him, but he seems very well.”
Saxon Warrior is joined by his year-older stablemate Cliffs Of Moher, who was third in the Hardwicke Stakes at Royal Ascot a fortnight ago, and Happily, who receives all the allowances as a three-year-old filly.
So far this season Happily has finished third in the 1000 Guineas at Newmarket and the Irish 1000 Guineas at the Curragh, as well as a close-up fourth in the French Oaks at Chantilly.
O’Brien added: “Happily is in good form. She had a very good run the last day and we’re looking forward to seeing her run.
“Cliffs Of Moher ran well in Ascot last time and we still think we haven’t seen the best of him yet. He’s been in good form since then.”
The Richard Fahey-trained Forest Ranger is unbeaten in two starts this season, following up his comeback victory in the Earl of Sefton at Newmarket with an assured display in the Huxley Stakes at Chester.
Fahey said: “Forest Ranger is in excellent form. He needs to step up on what he has achieved during his career so far, but he has won well on both of his starts this year.
“He should be a 20-1 shot and that probably reflects his chance, but he goes on any ground and we hope he is an each-way player.
“It’s a big ask, but whatever happens on Saturday, we’ll be finding out a bit more about him.”