It was one of the fears but not the largest of them and when Kauto Star was gently advised by his jockey Ruby Walsh that it was time to go, that the great and often astonishing adventure was over, a huge wave of relief rolled across the valley.
The applause was sustained and prolonged and quite detached from the race in which on more exuberant days the hero had made history and won the hearts of a people.
Kauto Star had cleared just nine of the fences that were once such frail obstacles to his brilliance but Walsh was sure that there was no more fire to be kindled, no more spirit to tap, and at the advanced age of 12 the equine hero walked away from the throng which had come to throw up one last huge communal salute.
Instead, they clapped their gratitude for the years that had gone but would never be forgotten and there was also, if we are very honest about this, a degree of celebration.
On the course that had taken the lives of five horses these last few days, there had been a largely unspoken concern that Kauto Star, given his courage and his sometimes unpredictable jumping, was in danger of becoming a sixth. It was an idea firmly, even angrily rejected by his connections but, still, you could almost taste the sense that the worst of it was no more troubling than that Kauto could no longer compete on the front line of the sport he had come to enrich not just with his performance but also his nature.
Kauto Star was an utterly authentic champion on the best of days. But he was also a drama waiting to happen, a misadventure about to unfold, or maybe a piece of extraordinary redemption.
Yesterday, there was no plot twist, no surge into unlikely terrain, only the acceptance that when he fell back home in Somerset a few weeks ago he had ruined his chances of winning back the Gold Cup for a second time. The first recovery, from Denman, made history; a second yesterday at the expense of defending champion Long Run would have touched the surreal.
But then it could also have been a shocking denouement and that it wasn't, that the new champion Synchronised – driven home with all the ferocious ambition that has become the trademark of A P McCoy – was saluted for his own magnificently combative nature without any shadow of tragedy, was cause enough for another round of cheers.
There was one overwhelming emotion and it is the one that comes with one deliverance or another – on this occasion that of a horse who had for so long lived perilously but quite brilliantly.
The King was gone from the scene of his greatest battles, not dead, so long live the new king – however briefly he reigns out on the course.
If Synchronised, trained by Jonjo O'Neill, who entered the folklore of racing when he brought home Dawn Run so dramatically in 1986, and owned by J P McManus, who has probably invested roughly the equivalent of the gross national product of a mid-sized banana republic in pursuit of racing's great prizes, is a brave and resilient champion, he is not likely to stir the imagination in the way of the retired Kauto.
Retired? None of his connections were willing to confirm that reality but there was indeed an overwhelming sense that Kauto was leaving the game in almost precisely, even uncannily, the same way as another great horse, the triple Champion Hurdle winner Istabraq here 10 years ago.
Walsh provided some reassurance when he said, "It didn't last long but the horse is all right".
Trainer Paul Nicholls (left), who had agonised over the running of Kauto for several weeks, then decided that he had once again restored himself to optimum running order, said, "Ruby reported that he jumped the water jump, stretched and then he said he wasn't with the horse so he pulled him up.
"We won't worry about whether or not this was the last run of his career. He has been a blinding horse, so we will turn him out during the summer and then see what happens. He is unlikely to run in a Cheltenham Gold Cup again.
"I will have a talk with Clive Smith [the owner] and I'm not going to make any rash decisions – he has been a wonderful horse and we will do what is best for him.
"Ruby has done what is best for him today as well and that is exactly what I asked him to do. Kauto Star has come back 100 per cent, absolutely fine, but obviously something is niggling him.
"We tried to get everything right but no matter what you do, you don't have the pressure of a race so until you run you don't know."
Yesterday Walsh, the most intuitive of horsemen, knew as soon as the pressure gauge was turned up a notch that Kauto could not hold his place, could not produce the smooth travelling that always presaged the most spectacular of his work.
Soon enough, it was clear that the young champion Long Run would suffer the same fate as McCoy kept asking questions of Synchronised – and invariably received the right answers.
In their wake, Walsh swiftly reached the same conclusion as had Charlie Swan aboard Istabraq a decade a ago.
Now, Istabraq is pampered by yesterday's winning owner McManus, who feeds the great horse fruit and even threw a celebration party to which the hero entered along a red carpet. The man from Limerick was among the first to pay tribute to Kauto yesterday. He said, "Now he can retire and lead a lovely life."
Kauto Star's owner Smith appears to be thinking similar thoughts. He said, "I think we will probably retire him. We said we wouldn't say anything today, that we would just see what happens, but I think that it [retirement] is a very good bet."
When he said that it was possible to fancy there was a murmur in the hills – and that it was saying Amen.