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".
27 March 2017Gevrey Chambertin one of four stars to bow out for David Pipe
Brian Ellison's Tonto and Walker primed for Lincoln challenge at Doncaster
Jonjo O'Neill's Box Office puts up winning display at Market Rasen
Ex-jockey Allan Mackay in hospital after fall on Newmarket gallops
Davy Russell booked by Tom George for Saint Are Grand National mount
Warren Greatrex maps out Aintree aims for Keeper Hill and La Bague Au Roi
Richard Johnson pays tribute to 'fantastic' Reve De Sivola
Arctic Fire pencilled in for Champion date at Punchestown
Morando among Lincoln acceptors for Roger Varian
Roger Varian looking to Coronation Cup for Postponed redemption
Arrogate takes a break as Breeders' Cup repeat remains ultimate goal
Toscanini joins Richard Fahey to act as Ribchester's pacemaker
End of an era as Ballymacoll dispersal sales announced by Tattersalls
Flying start for Aidan O'Brien as new Irish Flat season kicks off at Naas
Aidan O'Brien targets Dundalk comeback for unbeaten Classic hope Caravaggio
Sam Twiston-Davies and Paul Nicholls dominate at Wincanton
Anseanachai Cliste prevails in Ulster National thriller at Downpatrick
In-form Noel Fehily eager to take National chance on Blaklion
Park Express delight for Mick Channon and Graham Lee with Czabo
Mark Walsh to have Cheltenham injury progress assessed
Meade readies Aclaim for Lockinge bid
Martyn Meade has Craven Stakes in mind for Classic contender Eminent
26 March 2017Brendan Brackan back in style for Irish Lincolnshire victory
Moonlight Bay shows smart turn of foot to take Irish Flat season opener
Seeyouatmidnight called up for National service by 'delighted' Sandy Thomson
Saint-Cloud scorer Plumatic one to watch
Super Solow on the comeback trail for Freddy Head
'I can't believe he won' - Bob Baffert in awe of World Cup hero Arrogate
Snow Leopardess pounces at Newbury
Jack Hobbs oozes class in Sheema stroll
Death of three-time Long Walk hero Reve De Sivola at Kelso
Moreira advertises skills in saddle as Vivlos claims Turf
Biscuits swoops for sweet success in Golden Shaheen
Right result for French ace in Al Quoz as Limato struggles
Snow digs deep for UAE Derby glory
Vazirabad does it again in Dubai Gold Cup
25 March 2017Great Field looks set for great things after Thurles demolition
Brilliant Arrogate rules the World in Dubai
Late Summer charge is enough to land Godolphin Mile spoils
Fozzy Stack hoping for Dream start to training career in Irish Lincolnshire
Somehow bids for Express success on seasonal bow at Naas
Bullish Tom Symonds fancies Don Bersy to maintain hot streak at Newbury
Nicky Henderson has Punchestown in mind for Brain Power
Amateur rider James Ridley banned for 28 days in Newbury drama
Daryl Jacob hoping Gordon Elliott can work Natonal magic with Ucello Conti
Oliver Sherwood has Hitherjacques Lady ready to roll for Newbury test
Hugo Palmer targets Mile high with Gifted Master
Jim Crowley bowled over by Al Quoz Sprint hope Ertijaal
Heartbreak City chasing Dubai Gold for Tony Martin
Roger Charlton has Decorated Knight ready for Meydan Turf war
Roger Varian optimistic as Postponed challenges for Sheema Classic double
24 March 2017Double delight for Nicky Henderson at Newbury
Dermot McLoughlin forced to rule Vics Canvas out of Grand National
Bob Baffert wants to rule the World with awesome Arrogate
Charlie Appleby maps out Classic gameplan with exciting filly Wuheida
Coneygree going great guns for Sizing John showdown at Punchestown
Sam Twiston-Davies sides with Saphir Du Rheu in Grand National at Aintree
Jean-Claude Rouget stars Almanzor and La Cressonniere set for big 2017
Cheltenham ace Yorkhill heads Ryanair entries at Fairyhouse
Supreme ruler Labaik in great heart with Fairyhouse and Punchestown on the radar
'Slow process' as Toast Of New York continues to be assessed for racing return
Hopes high Derek Fox will return from injury to ride One For Arthur in National
Mags Mullins in no hurry to map out Debuchet plans
Enda Bolger hoping Aintree fences will fire up On The Fringe