Nicky Henderson will do all he can to get Altior to the Betway Queen Mother Champion Chase after revealing the brilliant two-miler was found to be lame on Sunday morning.
Altior suffered his first career defeat over jumps at Ascot in November, but bounced back on his return to his favoured two miles in the Game Spirit at Newbury last month.
All had been set fair for an eagerly-awaited showdown with Defi Du Seuil and Chacun Pour Soi at Cheltenham on Wednesday.
But on Sunday Henderson said: "Unfortunately Altior was lame this morning, due to an old splint that has been dormant. It's never bothered him before and typically it rears its ugly head now.
"We are working away and there's lots we can do, we have two days, but it's an uphill battle. We have the treadmill he can go on and it's very cold water, which helps these things a lot.
"We have to keep going. We're working away and we'll either get lucky or we won't."
He added: "He was sound as a pound yesterday - you wouldn't have seen a sounder horse."
