Yohan Cabaye, Serge Aurier, Lucas Moura and Marquinhos all went off injured during Saturday's Ligue 1 draw with Caen, with only the latter in with a chance of featuring in the last 16 first leg clash.
Whoever plays, Blanc expects the XI he puts out to be competitive.
"We will be without Yohan Cabaye, Serge Aurier and Lucas Moura," he told reporters.
"We will wait for end of training to see who's fit to play. Three won't be there and after practice there will be news on any others.
"Let's see how they feel and whether they feel ready because you can't play such a big game if you're not 100 per cent fit.
"The starting XI will be 100 per cent fit and competitive. [Thiago] Motta has experience and we really need him to be fit, [the Chelsea game] will also be a great test of maturity too for Marco Verratti. I think he will answer positively."
The quartet of injuries compounded a difficult day on Saturday as PSG threw away a two-goal lead in the latter stages against Caen, leading to criticism in the French media.
"Saturday was a catastrophe but every time something's negative at PSG I'm always held responsible," added Blanc.
"I'll happily take responsibility if it means my team is more focused but everything that can happen I'm always responsible - C'est la vie.
"If you say you worry about me giving everything for the team tomorrow then that's the way it's going to be but I'm disappointed you guys think that."
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