Currently a top-priced 14-1, he is regarded as being no more than 50-50 to get to the Festival, after bruising a hock.
He was certain to start favourite for the Hennessy at Leopardstown on Sunday week, but misses that race now.
Speaking on At The Races yesterday, Pandorama’s owner, Robert Bagnall, revealed: “We think he got a knock in his box at Noel’s yard. We brought him out for a small canter on Friday and he came back slightly lame.
“Over the weekend, we walked him and he appeared to be alright, but when he brought him out this morning he came back lame again and the problem seems to be that he has bruised his hock.
“We did an x-ray on the horse and at first it appeared to be a little crack in his hock, but we x-rayed the other hock as well and it was identical. We are hoping that it is just bruised but, obviously, he will miss the Hennessey.”
Bagnall continued: “It is my lifelong ambition to get to Cheltenham and Noel thinks that it is just a temporary setback that he should get back into training and come alright. He thinks the chances are a good 50-50 that we will get him there.
“It is just very unfortunate, so we hope and pray that it might be just a temporary setback and we will get him to Cheltenham.
“It is definitely not career-threatening, but on the other hand it could be season-threatening, if it is anything more serious than bruising. Within a week we should know for certain.”
Pandorama has run twice this season, landing the Grade 1 Lexus Chase at Leopardstown by six lengths on his most recent start, having been pulled up in the Hennessy at Newbury on his seasonal reappearance.
Following the news that Pandorama will miss the Hennessy, Paddy Power make Pride Of Dulcote their new 13-8 favourite, with Joncol next at 11-4.
William Hill offer 6-4 Pride Of Dulcote and 3-1 Joncol. Boylesports bet: 13-8 Pride Of Dulcote, 5-2 Joncol, 8-1 Money Trix, 9-1 Cooldine, 12-1 bar.