Mighty Man, a general 20/1 chance for the RSA Chase at Cheltenham, has been ruled out after sustaining a season-ending injury.
The top-quality staying hurdler was sidelined for two years with a tendon problem but had started to make into a fine novice chaser, impressing at Huntingdon this week with some spring-heeled leaps.
"He fractured his sesamoid and is going to be operated on this afternoon," said trainer Henry Daly.
"He had a tiny little nick after the race but we just felt it this morning. We put him in a box, took him off to the vets and they called me back.
"The vet seems confident that it is certainly not life-threatening or even career-threatening, the only problem is he's already 10."
Henrietta Knight's exciting novice Somersby continues his education over fences in the Lindley Catering Novices' Chase at Hereford tomorrow.
Last season's Supreme Novices' Hurdle third is two from two since tackling the larger obstacles and proved much too good for the smart Crack Away Jack in the Grade Two Henry VIII Novices' Chase at Sandown last month.
"All is well with him and we're looking forward to getting him back on the track," said Knight.
"Hopefully he'll have a nice run round and learn a bit more about his job."
Next month's totesport Trophy at Newbury is on the agenda for Mamlook following his impressive success at Ascot last weekend.
Having run a fine second in the Cesarewitch at Newmarket last October, the six-year-old then chased home last season's Champion Hurdle runner-up Celestial Halo on his return to hurdles at Wincanton.
He made the most of his light weight to win the Grade Two Holloway's Hurdle last Saturday and trainer David Pipe will now drop him back to the minimum trip at Newbury on February 13.
"I think it's the plan to go there. He's gone up 7lb in the handicap but goes to Newbury with a 5lb penalty," Pipe said.
"He's come out of the race in good form and obviously he's going back to two miles, but he's pretty versatile regarding trip."
Skippers Brig is on course to run at Ayr next month before a tilt at the William Hill Trophy at Cheltenham in March.
Nicky Richards' inherited the chaser due to the retirement of Lenny Lungo and on just his third start for the yard, he finished third in the Boylesports Gold Cup behind Poquelin.
The Peter Marsh at Haydock last weekend had been the plan but Richards suffered more than most at the hands of the weather and despite moving a portion of his string down to Newmarket, Skippers Brig was slightly behind schedule.
"He goes to Ayr on February 13 (victorchandler.com Handicap) and hopefully if we get a wettish spring, which we may not do, he'll go to Cheltenham for the three-mile handicap there," said Richards.
"That race could suit him but if it dries out, he won't go anywhere. He's got to have cut because he's a giant of a horse.
"He's got plenty of pace for a big horse but when we stepped him up to top-class handicapping, he just needs that extra half-mile.
"He won over three miles for Lenny Lungo last season. I'd say he'd stay all right, he came up the hill well at Cheltenham, he wasn't stopping.
"Any sort of handicap race you are in the lap of the gods though."