Circus Maximus, sixth in the Derby behind stablemate Anthony Van Dyck, has been added to the St James's Palace Stakes field after his Aidan O'Brien stablemate and 2,000 Guineas winner Magna Grecia was ruled out of the race.
The Sussex Stakes at Glorious Goodwood is the new plan for Magna Grecia after the 2,000 Guineas winner failed to recover from a torn hamstring in time to take his chance in the St James's Palace.
O'Brien said on Wednesday: "We thought it was worthwhile to supplement Circus Maximus for the St James's Palace Stakes as he has been in great form since the Derby.
"When you look back on his form from last year over a mile, he wasn't too far off the best of them at Doncaster in the autumn so we think he should be fine over a mile. We felt it was the right thing to do and, as I said, he seems in great form."
Magna Grecia had been a 4-1 shot to exact revenge on Phoenix Of Spain for his defeat in the Irish 2,000 Guineas at the Curragh, the race in which he picked up the injury, but O'Brien has decided the opening-day test will come too soon.
"Magna Grecia is nearly 100 per cent but he won't be back in work until next Monday so we just ran out of time with regard to Royal Ascot," he said.
"It took a bit more time than we thought but he is recovering well. The Sussex at Goodwood would like an ideal race to target him at now, but we will see how Monday goes and take it from there."
Arizona, eight-length winner of a Curragh maiden looks set to lead O'Brien's Coventry Stakes team on day one of Royal Ascot as the trainer bids to win the race for an unprecedented ninth time.
O'Brien, whose most recent success was with Caravaggio in 2016, said: "Arizona is a lovely colt and we were very happy with him last time at the Curragh. He took a nice step forward from his first run and he seems in good form since then. We think the Coventry is the race for him."
There were 37 entries left in the Coventry at Wednesday's latest forfeit stage, with O'Brien responsible for nine of them.
Ten Sovereigns was cut into 6-4 with many firms for the Commonwealth Cup following the fatal injury to Lady Kaya during a routine gallop on Tuesday and O'Brien reports the colt to be be on track for the 6f event.
"Ten Sovereigns seems to be in good form and we are happy with him since Newmarket. The Commonwealth Cup remains the plan for him," the trainer said.
Magical is set to bid for a four-timer in Wednesday's Prince of Wales's Stakes, many people's idea of the race of the week. O'Brien said: "Magical has done nothing wrong all season and we have been very happy with her. The Prince of Wales's Stakes is the race we are looking at for her."