Nube Negra has been left to head the British opposition to Tingle Creek Irish favourite Chacun Pour Soi after Shiskin was removed from the race by Nicky Henderson.
The unbeaten chaser was due to make his seasonal reappearance in the Sandown Grade 1, but Henderson does not feel he is quite yet at concert pitch.
As a result he will now head for the Desert Orchid Chase at Kempton over Christmas instead.
"I've just spoken to (owner) Joe Donnelly and we've sadly and reluctantly decided that Shishkin is not going to run in the Tingle Creek," said Henderson.
"There's nothing wrong with him, but I just haven't got there. He worked this morning and he just isn't sparky at the moment. I think I just got behind the ball a little bit.
"We did his wind in the autumn which wasn't a problem, but it just put us behind the ball and Nico (de Boinville, jockey) and I both feel he's not quite on his A game.
"It really is a thin line. We've scoped him and everything and there's nothing wrong, but you can't afford to go into this (at) anything bar 100 per cent."
Henderson told PA: "Joe is a fantastic man and he said to do whatever is best for the horse and that is definitely what we're doing.
"Sadly he won't be there and this race is sort of ill-fated for us at the moment.
"We'll go to Kempton now, I imagine. He looks magnificent, he's just missing maybe five per cent that you need to have and can't go without.
"We all know that the best thing for this horse is to give him a chance, so sadly he won't be there but he'll be around for Christmas."