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".
31 August 2016Double tops at Bath for Georgia Cox
Richard Hannon appoints Silvestre de Sousa for Ventura Storm St Leger ride
Franny Norton strives for Mersey paradise with Sprint Cup hope Dancing Star
Darren Bunyan has Mill Reef aim for Curragh scorer Hit The Bid
Elliptical thrown in at the deep end in Poole poser at Salisbury
Mark Johnston to step Kilmah up in class after Goodwood success
Franny Norton comes in for ride on Sprint Cup contender Dancing Star
German Guineas hero Knife Edge sold to race abroad
Simon Crisford considers Mill Reef at Newbury for exciting Mokarris
Uxizandre closes in on return to training
Irish Champion Stakes bid "very possible" for star filly Minding
Bryan Smart considers Newbury option for Beverley Bullet hero Alpha Delphini
Tony McCoy not expecting ITV call
Royal Lodge among potential targets for Seven Heavens after Goodwood romp
Easy ground expected for Sprint Cup at Haydock
Park Stakes at Doncaster emerges as potential target for Librisa Breeze
Lady Aurelia enjoying Newmarket spell ahead of Cheveley Park mission
Desert Water makes winning start at Goodwood
Charlie Hall at Wetherby a possible starting point for The Last Samuri
Kevin Ryan has no Leopardstown going concerns for The Grey Gatsby
David Lanigan cool on Almodovar Kempton charge
Order Of St George nominated by Aidan O'Brien for Melbourne Cup
30 August 2016Epsom first for Ivan Furtado as Nouvelli Dancer strikes again
Seven Heavens maintains unbeaten record with Goodwood romp
Mitchum Swagger set to sidestep Superior Mile at Haydock
Owen Burrows targets Doncaster heat for exciting juvenile Akhlaaq
Mick Fitzgerald secures ITV racing role
Willie Mullins gives Ebor defector Ivan Grozny time to recover
'Magic horse' Clondaw Warrior on the march for Melbourne
Jamie Codd savours Amateur Derby glory at Epsom
Four-star Silvestre de Sousa back in pole position in championship race
Alicante Dawn makes it a Ripon season to remember for Bryan Smart
Limato back in Sprint Cup picture as Quiet Reflection primed
Owen Burrows plots path for Markaz after German delight
Trainer David Wachman to retire at the end of the season
Time Test to swerve Irish Champion Stakes at Leopardstown
Frankel colt Seven Heavens ready for Goodwood test
Charlie Appleby to choose between Leopardstown and Ascot for Hawkbill
29 August 2016Snow Falcon freezes out Roscommon rivals
Irish ace Jamie Codd sparkles in Amateur Derby at Epsom
All-the-way Alicante Dawn too hot for Ripon rivals
Careless riding ban for Joe Fanning in amended Newcastle result
Richard Fahey and Paul Hanagan strike at Ripon
Four-star De Sousa fires Hurricane warning at Epsom
Dancing Star and Mehronissa added to Sprint Cup field at Haydock
Unlucky break for Andrew Lynch at Cork
5 things you might not know about Jim Crowley
Title-chasing jockey Jim Crowley living the 'dream'
Henry Candy could draw stumps with Windsor winner Chain Of Daisies
Ger Lyons set to bid farewell to Australia-bound Endless Drama
Henry Candy puts Limato back in Haydock Sprint Cup contention
32Red continues support of All-Weather Championships
Pulled muscle could derail Middle Park plans for Caravaggio
Intelligence Cross towers above Curragh rivals
Opal Tiara sparkles in Supreme Stakes at Goodwood
Somehow far too good in Snow Fairy waltz at the Curragh
Sea Of Grace battles to Flame Of Tara success for John Oxx
Ruby Walsh back in business at Cork
Dermot Weld on weather watch for Harzand in Irish Champion
Muthmir team 'disappointed' as classy sprinter misfires in Beverley Bullet
Thikriyaat to undergo tests after Goodwood reverse
28 August 2016Robbie Hennessy stalwart Rubi Light retired
Regally-bred Yucatan off the mark at the Curragh
Richard Fahey feels Queen Kindly can savour mile high
Ground key to Boynton as Charlie Appleby ponders Curragh raid
Roger Charlton ponders Newmarket challenge with Frankel filly Fair Eva
Richard Fahey expects Ribchester progress in QEII at Ascot
Marco Botti has Gowran in mind for Haydock scorer Aljazzi
Jim Crowley takes the lead in jockeys' championship battle
Chain Of Daisies too strong in Winter Hill test
Lightning strikes in Celebration Mile
Wind too fast for Hopeful opponents at Newmarket
Platitude a class apart from March Stakes rivals
Alpha Delphini hits the target in Beverley Bullet for Bryan Smart
Certificate stamps authority on Goodwood handicap
Kilmah battles hard to land Prestige prize
Australian jaunt confirmed for Scottish after Strensall win