Having provided the trainer with a first Festival win last March, Willoughby Court was favourite to strike again in the JLT Novices' Chase.
However, Pauling revealed on Monday that the seven-year-old had pus in a foot and time is ticking away.
"Every day that goes by is another day we are missing. It is getting very close and, in all honesty, he is not the sort of horse I am going to take there unless I am 100 per cent happy," said Pauling.
"I'm afraid pus in the foot is a very insignificant injury long term, but short term it can be quite sore and slow you down considerably. You don't want to work a horse which is favouring one leg over another otherwise they might get an injury.
"It's look scarily like we are struggling. I would say it is 70-30 against him running at the moment. I'm not going to risk a horse of that ability.
"Believe you me, having a horse that is favourite for the JLT is not something you want to give up, but at the same time you have to be realistic about it. You also have to think about the long-term future of the horse.
"I've no reason to believe he wouldn't be firing on all cylinders for Aintree and there is a two-and-a-half-mile novice there. That might be even more competitive as a lot of the two-milers are stepping up.
"You can't get too down as this is the game and I'm not the only one it has happened to."
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