The Grade One Tingle Creek Chase at Sandown on Saturday suffered a significant blow on Wednesday evening when Un De Sceaux, the odds-on favourite, was ruled out of the race by Willie Mullins, his trainer.

Mullins broke the news on Wednesday evening, describing the Arkle Trophy winner as a “little flat”.

Un De Sceaux has also been ruled out of an alternative engagement in the Hilly Way Chase at Cork the following day after failing to convince his trainer that he is ready to return to action. “Unfortunately Un De Sceaux will not run this weekend,” Mullins told the Racing Post. “He has been a little flat in himself the last two days.”

The Tingle Creek is often the most competitive and high-class two-mile chase of the season prior to the Queen Mother Champion Chase at Cheltenham in March but the loss of Un De Sceaux is a further blow to this year’s renewal after Sprinter Sacre, the 2013 Champion Chase winner, failed to appear among the five-day entries earlier this week.

Un De Sceaux had been expected to start at around 4-7 to win on Saturday but in his absence the market is now headed by Vibrato Valtat, from the stable of the champion trainer, Paul Nicholls. The grey, who won the Henry VIII Novice Chase over course and distance on the same card last year, is 7-4 while Simonsig, a stable companion of Sprinter Sacre at the Nicky Henderson yard, is 7-2.

Sire De Grugy, the 2014 Champion Chase winner, is 5-1 to return to winning form after a disappointing seasonal debut, along with Special Tiara, a Grade One winner at the track in April. The remaining possible runners are priced up at 14-1 or bigger.

The chance that Coneygree, the Gold Cup winner, will run over Christmas appeared to recede slightly on Wednesday, when Lady Oaksey, a member of the partnership which owns Mark Bradstock’s chaser, said that the King George VI Chase at Kempton on Boxing Day or the Lexus Chase at Leopardstown on 28 December could “come too soon” after Coneygree suffered a minor setback last month.

Coneygree was an impressive winner on his return to action in a minor race at Sandown in early November but missed an intended in run in last Saturday’s Hennessy Gold Cup after losing a shoe at exercise and suffering a bruise to his foot. “He’s a very fragile horse and has long legs,” Lady Oaksey said.

“The longer the legs, the more problems they have and I would think but I could not guarantee that [the King George] would come too soon. There is also the Lexus but that is only two days after the King George and could also be a bit too soon. The horse needs to get fit and then he’ll tell us when he’s ready. If we didn’t run [over Christmas], there’s the Denman [Chase at Newbury in mid-February] or the Cotswold Chase [at Cheltenham in late January]. Quite honestly, though, his main aim is the Gold Cup [in March].”

Paul Moloney, who has finished in the frame in the last seven runnings of the Grand National, faces a significant spell on the sidelines after he suffered a suspected broken leg in a fall at Ludlow on Wednesday. Moloney, who was riding Kudu Country for his main employer Evan Williams, fell at the first in a handicap chase.

“He’s on his way to Hereford hospital,” Williams said afterwards. “He’s broken his leg below the knee. I’m absolutely gutted for him but he couldn’t be in better hands. Obviously we’ll know more in time.”