The duo missed the first leg after testing positive for Covid-19.
However, they are now out of isolation and are due to return to training.
But Tuchel admits he does not know if they will be ready to be involved.
Apart from Kante and Silva, Chelsea have no fresh injury concerns or Covid-19 cases ahead of the match.
Tuchel said: “Their cardiac tests, negative, of course, Covid tests, but you also have to follow some protocols to bring them back to training.
“I don’t know (if they are ready). I have to wait if they are in training and then let’s see how they respond to the training.
“It’s a gamble. If we do it, it’s a gamble and I’m not sure if we do it and how much of a responsibility we can take there. But we have to do it step by step, I’m not in the moment even sure if they will come to training.
“If they come to training, we have to see the reaction and then decide then.”