Chelsea will make a late decision on N’Golo Kante and Thiago Silva ahead of Wednesday’s Carabao Cup semi-final with Tottenham.
The duo missed the first leg after testing positive for Covid-19, but are now out of isolation.
They were due to take part in training at Cobham on Tuesday afternoon, but Thomas Tuchel admits he does not know if they will be ready to be involved.
Chelsea have no fresh injury concerns or Covid cases ahead of the match.
But Tuchel will assess Kante and Silva before deciding wheth to include them in his squad.
He 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 come to training.
“If they come to training, we have to see the reaction and then decide then.”
Tuchel insists there is no danger of complacency for the second leg, despite his side holding a 2-0 lead in the tie.
He added: “I would actually say we have no foot in the final, none of the teams, whether it half a foot or a whole foot, there is no need to waste energy over these things.
“We play another tough match in a tough stadium against a very good team and a top, top, top coach so we need to be prepared.
“Maybe it is better not to expect too much because nobody knows what is going to happen. We need to be fully aware of everything and to adapt to the situations that happen on the pitch.
“Of course we want to control the match and attack as much as possible, we had a very good match in the first leg but it is over, it is the past and we expect the best possible Tottenham side.
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“We prepared in the best manner, we did for the first match and we will do it again for tomorrow. We have to be spot on, forget the first result and do it again.
“I have trust in me, my staff and also my team and players. This is what we are used to, to arrive well prepared or you have no chance to win consistently or on that level. We have proved it, that is why we can allow ourselves to trust on this one, that we have our attitude right and then we will have the game right.
“I guess that everybody knows that we play a very important match in a derby against Tottenham, big stadium, big club and a very competitive coach on the other side so we need our best level.”