Trainer Paul Nicholls was dealt a huge double injury blow on Monday evening by the news Big Buck's and Al Ferof are set to miss the rest of the season.
The former was due to run in Saturday's Long Walk Hurdle at Ascot, while Al Ferof was being prepared for an assault at the King George VI Chase at Kempton on Boxing Day.
Nicholls told Betfair: "At evening stables, we discovered a problem with both Big Buck's and Al Ferof. I am not in a position to go into great detail at this point, but I can confirm that Big Buck's will not be taking up his engagement at Ascot on Saturday and Al Ferof will not be running in the King George."
Big Buck's' owner Andy Stewart said the remarkable nine-year-old, who has won his last 18 races, has suffered a leg injury and would not defend his crown in the Ladbrokes World Hurdle at the Cheltenham Festival next March.
He told Press Association Sport: "He didn't do it (sustain the injury) on the gallops. He was a little bit anxious in one of his legs at evening stables and after Clifford (Baker, Nicholls' head lad) and the vet inspected him, we decided to draw stumps. He'll not be running on Saturday and he won't be trying to win a fifth World Hurdle in March.
"I'm a little bit gutted, but no-one has died and the horse is perfectly well. When the horses come back in at the end of July we shall reassess the situation. If he hasn't got that zest and sparkle, he will be retired."
Al Ferof, a fine winner of the Paddy Power Gold Cup at Cheltenham in November, has damaged a tendon and will miss the rest of the season, said owner John Hales.
"We were all set for the King George, but things like this are part of the game. We don't know how he got the tendon injury, but that's him out for the season. We'll obviously get him reassessed by the vet, but you can bet your life the King George and then the Gold Cup will be the plan in 12 months' time.
"He's still a youngster and has age on his side."
Nicholls later tweeted neither Big Buck's nor Al Ferof had sustained career-threatening injuries and that they "both will be back".
21 October 2014Power team weigh up options
Bangor cancel schooling card
No rushing back for Long Run
Dynaste leads Old Roan contenders
Grands Crus retired
Exciting Berlais heads to Chepstow
Force handed Hong Kong mission
Park favourite for Trophy hunt
Al Kazeem team eye Hong Kong trip
Commemorative bound for Breeders'
Slade eyeing victorious swansong
20 October 2014Chelmsford City handed 58 fixtures
Alderwood to take two-mile test
Dynaste leads Old Roan contenders
Hennessy aim for Clouds
Fiesolana on Breeders' trail
High-class possibilities for Trophy
Chelmsford City handed 57 fixtures
French option for Maarek
Billy back for chasing bow
Judge to bid for Breeders' glory
Pipe mulls Moon target
High hopes for Holywell
Judge in Breeders' frame
Hill stars for Stoute and Moore
Gabriel lifts Garnet for Deegan
New One back with a win
Light career hangs in balance
Stars shines on hurdling debut
King big guns ready to start
Tullius camp consider options
Doyle unlikely to appeal Ascot ban
Mullins prepares formidable team
19 October 2014New One breezes to victory
Lavelle has Becher plan for Lodge
Riches heading on road north
Down Royal plan for Tiger
New makes Kempton return
Panther hunting Canadian prize
Sun takes a shine to Cork
Hobbs upholds Showcase record
Another gold strike for Bronze
Gallant Noble a true Champion
Head turns on Charm in QEII
Madame is Ascot leading lady
Forgotten rules for Weld
Byron is poetry in motion
18 October 2014Forgotten rules for Weld
War misses Breeders' date
Rakti reaps Caulfield reward
Chatez bids for Balmoral crown
Lavelle duo top Cheltenham card
Integral takes on the boys
Noble on Champion mission
Belardo a Dewhurst sparkler
Together stands firm for Ballydoyle
Ivawood felled by plucky Thought
Crowley doubles up on Berkshire
Tendon injury sidelines Tent