French star Cirrus Des Aigles will not lock horns with Frankel in the Juddmonte International after failing to to recover from an ankle injury.
Last year's Champion Stakes hero added to his Group One tally in the Dubai Sheema Classic and the Prix Ganay earlier this year, but was narrowly beaten by Golden Lilac in the Prix d'Ispahan at Longchamp on his last start.
Trainer Corine Barande-Barbe had been looking forward to seeing her pride and joy take on the world's highest-rated racehorse on the Knavesmire on August 22, but he could now be re-routed to the Red Mills Irish Champion Stakes at Leopardstown on September 8.
"The cut he sustained to his ankle was a very deep one which quickly became infected and the wound took longer to heal than I had hoped," the trainer said.
"I kept him walking every day but I didn't want him to gallop on the sand while he was still recovering and, although he is working again now, there won't be enough time to get him ready for York.
"It is a great shame as I was looking forward to running him there (at York), but there are other races for him and I will now try to get him ready for Leopardstown.
"After that, there is Ascot, or I may look for a race at Longchamp on Arc weekend.
"He has recovered well from the injury and I have no doubt that he will come back as good as ever but we have just run out of time."
Planteur, by contrast, faces the daunting task of crossing swords with Frankel after being withdrawn from the Sky Bet York Stakes on the Knavesmire last month.
Marco Botti's top-class middle-distance performer was a leading fancy for the Group Two contest but after walking the track, connections felt conditions were too fast and decided not to run.
Botti admits it was a frustrating scenario and it now means that provided the ground is deemed suitable, he is likely to meet Frankel at York.
"We decided to pull him out because we just felt the ground was too quick and we didn't want to take a risk," said Botti.
"It was a shame as it looked a good opportunity for him and it was the right race, but it was just one of those things.
"The intention has always been to run him in the Juddmonte International and as long as the ground is right for him there, he will probably run.
"I'm not saying he needs soft ground, but he likes a bit of juice in the ground and fast ground is not for him.
"He will run wherever the ground is right and obviously we are going to meet Frankel if we go to York.
"If we think the ground is too fast again, he has the option of the Irish Champion Stakes, so we will see."