Colin Tizzard hopes to have Thistlecrack back on a racecourse around Christmas time after a season-ending tendon injury saw him become the latest high-profile name to be ruled out of the Cheltenham Festival.
The dominant force in the staying hurdle division last year, the nine-year-old won his first four starts over fences, including a scintillating victory in the King George VI Chase at Kempton on Boxing Day.
Despite suffering a narrow defeat at the hands of the ill-fated Many Clouds in the Cotswold Chase at Cheltenham at the end of January, he remained at the head of the betting for the Timico Gold Cup on March 17, but will not line up at Prestbury Park.
Tizzard told Press Association Sport: "Thistlecrack is out for the season, unfortunately.He had a bit of heat in his leg last night and was a bit sore.
"We had the leg scanned this morning and he has a slight tear on his tendon.
"We've seen it at every yard and it happens every year."
He added on At The Races:"We know it's not very serious, we haven't done much with him since the Cotswold Chase because he had a hard race, he had a little cough afterwards and got a bit light so we were just cantering.
"We hadn't done any fast work with him, we thought we'd give him a busy week this week. Obviously it stems from the race, but that's racing, that's horses for you.
"It's not very bad, it's not like breaking down, it's just a little bit sore there, a bit of heat.
"I asked the vet 'are we talking about next season off?', or are we talking about from Christmas on and he'll be fine, and he said he should be absolutely fine by Christmas, to have him back on a racecourse by then.
"It's not that we're going to miss next season, but things change. I'm as sure as I can be, he should be fine for next season from Christmas on."
The news comes as another huge blow to National Hunt racing's showpiece meeting, with Thistlecrack joining the likes of Coneygree, Annie Power and Faugheen on the sidelines.
Jockey Tom Scudamore has ridden Thistlecrack to 10 of his 13 career victories, and said the news made him "feel sick".
He said: "Joe (Tizzard) rang me on my way to the races and he just said he'd done a tendon and wouldn't be going to Cheltenham. From what I gather he'll be back next season, I've just been told he won't make the Gold Cup.
"It's something that happens in racing unfortunately, look at Willie Mullins this season, he's lost a handful. Even still, it doesn't make it easy to swallow, it makes you feel sick.
"It's worse for the owners, John and Heather (Snook), and the lads that see him every morning.
"With good horses you want them to peak on the big days and that's Cheltenham, fortunately we won there last year and the King George this season.
"Look at Olympians, they get their dreams shattered and have to wait four years, hopefully we'll get another chance next season."
John Snook admitted it came as a bitter blow when he received the phone call all owners dread.
He said: "It's very disappointing, but it's one of those things that happens with horses. We've got to stop and that's that.
"They just found a little bit of heat in his leg and it might be that he feels better in a week or two, but you'd be risking everything if you carried on.
"We all get our fair share of bad luck. We've seen it happen to Willie Mullins with the likes of Annie Power and Faugheen, and of course Oliver Sherwood after what happened to Many Clouds.
"Whether it's JP McManus, Rich Ricci or ourselves, we all want to get our horses to the Festival and when something like this happens it knocks the stuffing out of you, but there's nothing we can do about it.
"Hopefully we still have a horse. We've got to stop and we'll find out where we are in about eight months' time."
Despite Thistlecrack's enforced absence, Tizzard still has a formidable hand for the Festival showpiece.
Paddy Power make Thistlecrack's Hennessy Gold Cup, Welsh Grand National and Denman Chase-winning stable companion Native River the new 5-2 favourite, just ahead of fellow Venn Farm inmate Cue Card at 3-1. Ladbrokes go 11-4 about Native River.
Tizzard said of Cue Card and Native River: "They have been doing a wonderful job in the last week or 10 days. They are fit and well, but we've all seen it, everyone dreads when you train horses at any time, but it seems to me when you run up to Cheltenham some little gremlins get in, don't they.
"We've had worse things happen in life, he's won four races this year and we should have him again by Christmas, it's just so disappointing for everybody. Everybody wanted to see him run at Cheltenham."
Snook will now be cheering on the other Tizzard runners in the Gold Cup and still has high hopes of a Festival winner of his own, with Thistlecrack's half-brother West Approach bound for either the Albert Bartlett or the Stayers' Hurdle.
"When you think we've lost Vautour, Many Clouds and now Thistlecrack - they are three horses who could have all played a major part in the Gold Cup," Snook added.
"I'll be hoping Jean (Bishop, owner of Cue Card) or Anne and Garth (Broom, owners of Native River) can win it - a dead-heat would be great.
"We still have his little brother, West Approach. He's in the two races and the Albert Bartlett is probably the more likely.But if something happened to one or two of the top horses in the Stayers' Hurdle, who knows?"