The eight-year-old came down at the second-last fence in the Paddy Power ’So Quick, So Easy iPhone App’ Chase when making all the running to that point and looking likely to justify prohibitive odds of 1-4.
He had also taken a tumble on his chasing debut, but in between the two blips had been peerless in four starts that had yielded a hat-trick of Grade One triumphs.
Walsh admitted being unable to get into a rhythm on the Willie Mullins-trained gelding that day – but has been delighted with his homework since then.
The rider said: “We just felt he was a bit buzzy on the day, it was hard to get him in a rhythm.
"He was standing too far back at some and getting in too deep at others, I was just never in a good rhythm with him.
“I couldn’t have been happier with him before he fell, I was travelling really well, I saw a stride and asked him, but he changed his mind.”
Walsh admits Sire De Grugy sets a standard Un De Sceaux has to meet.
He said: “He’s schooled really well since, his work is good, we’re happy with him and Sire De Grugy is a new challenge for us. He sets a standard and we have to get up there.
“We’re happy and we’re looking forward to it.
“He likes what he does, he’s brave, he likes to get on with it and attack fences, I enjoy riding him but the margin for error is quite small.
“I think he’s a thrilling horse to ride.”
Sire De Grugy should prove a proper adversary for Un De Sceaux, having won this race in 2014 as well as the Champion Chase.
After a mixed last campaign, the 10-year-old has been in fine form this winter winning the Tingle Creek at Sandown for a second time before just losing out in a terrific duel with Sprinter Sacre in the Desert Orchid Chase at Kempton.
Trainer Gary Moore believes he has Sire De Grugy in tip-top shape.
“He is in great order and as good as can be expected, so it’s fingers crossed. If anything he is a fraction better than last time,” said the West Sussex trainer.
“He’s better in softer ground, he makes soft ground look like good ground. It would definitely make his chances better – I think I’ll be the only one praying for rain at Cheltenham.
“I’ve got great respect for Un De Sceaux, what he did last year was unbelievable, and he is the one to beat, but if don’t try you don’t know.
“The confidence I have in my horse could not be any higher, I am very confident – whether that is good enough to win, we won’t know until Saturday.”
Moore also saddles Traffic Fluide, who made giant strides as a novice last season, winning at Plumpton and Sandown before finishing third to Sizing Granite in the Grade One Maghull Novices’ Chase at Aintree on his final start in April.
Vibrato Valtat was far from disgraced in third place behind Sprinter Sacre and Sire De Grugy at Kempton and his trainer Paul Nicholls is convinced the grey will not be out of place.
“He probably ran to his best at Kempton the other day behind two Champion Chase winners,” Nicholls said.
“This horse has come from being a 121-rated hurdler to being on the fringe of a Grade One horse and actually winning a Grade One last year.
“He’s running this weekend and the more testing the ground, the better it will help him.
"He’s a good, solid horse who gives his owners a lot of fun without being a proper Grade One horse.