Trainer Nicky Henderson will decide tomorrow morning whether Queen Mother Champion Chase favourite Altior will make the race.
The eight-year-old, who is unbeaten in seven starts over fences, has lameness in his leg on the eve of the Cheltenham Festival.
The Henderson yard remain confident that Altior will still be able to oppose Min and Douvan in Wednesday's feature and says there will be careful treatment administered overnight.
"Altior was unfortunately lame this morning in his near fore leg and we have located some pus in the frog. He was still able to exercise in the water treadmill this morning, which he regularly does anyway, and a poultice will now be applied and left on overnight to draw out the pus.
"The foot will also be 'tubbed' at regular intervals and the shoe will hopefully be replaced first thing tomorrow morning.
"Both our vet and farrier are working very hard and are more than hopeful that he will even be able to canter tomorrow and therefore confident he will be clear to race on Wednesday.
"Obviously we will monitor the situation and keep everybody up to date with his progress but there will be nothing more to say until tomorrow morning."
Trainer Willie Mullins / INPHO/James Crombie
Willie Mullins confirmed that both Min and Douvan will oppose Altior in the race with Ruby Walsh set to take the mount of Douvan while Paul Townend will go on Min.
There had been suggestions that owner Rich Ricci wanted Douvan to instead go in the Ryanair to avoid a clash with stablemate Min but Mullins says jockey Ruby Walsh had the final call.
"Ruby has been very happy with Douvan in recent days and was keen to ride him in the Champion Chase rather than in the Ryanair. That made my mind up and Rich Ricci was happy with that."