Altior remains in the running to defend his crown in the Betway Queen Mother Champion Chase at Cheltenham on Wednesday.
Nicky Henderson announced on Sunday morning the brilliant two-miler was lame, after a dormant splint that had caused no problem to the 10-year-old previously “reared its ugly head”.
Work on a water treadmill has helped, and the Seven Barrows trainer told the PA news agency on Monday: “We have declared this morning. He has improved considerably. He would not be able to run today, but we have got 48 hours.
“If it continues to improve as much as it has done since last night to this morning, he’s got every chance.
“We have to give him every chance, it’s only right. I’ve been in touch with the British Horseracing Authority vets as well, we’ve kept them informed all along – David Sykes (BHA) is in the loop.
“If it was today, no you wouldn’t (run), but the improvement has been significant enough to justify leaving him in and seeing how we are going tomorrow. If necessary we’ll have to take it to the wire.”
He added: “He’s nothing like as touchy on the splint today as he was yesterday. When you pressed it he was sore, but he’s much less reactive today and he is much sounder.
“I think a lot of it is he actually needs to sort of get a bit of belief in himself again, he’s been sore for 48 hours – it’s nothing like as sore, so the horse just needs to believe.
“He’s exercising and is in the treadmill again and can do plenty of work in that. We can do plenty of work in there, which keeps everything moving.”
Beaten for the first time over jumps at Ascot in November, the Patricia Pugh-owned gelding returned to his best in the Game Spirit Chase at Newbury last month.
Should he line up, Altior will be bidding for his fifth win at the Festival, having taken the Supreme Novices’ Hurdle and Arkle Trophy before his two Champion Chase victories.
Defi Du Seuil has been the new kid on the block this season and he heads Altior’s opposition. Last year’s JLT Novices’ Chase victor has won all his three starts this winter.
Philip Hobbs’ seven-year-old has captured the Shloer Chase, the Tingle Creek and the Clarence House Chase to stake a big claim for the coveted prize.
Willie Mullins’ Chacun Pour Soi is the sole Irish contender, but is highly regarded and he did beat Defi Du Seuil by four and a quarter lengths in the Ryanair Novice Chase at Punchestown last May.
The eight-year-old showed his well-being when taking the Grade One Ladbrokes Dublin Chase at Leopardstown last month.
Paul Nicholls is represented by Dynamite Dollars and Politologue, who was runner-up to Altior 12 months ago.
Last year’s third home, Sceau Royal, does battle again for Alan King and the Tom George-trained Bun Doran completes the septet.