The Ligue 1 champions were swept aside by Barca last week meaning they must score at least three goals in the return leg to have any chance of making the last four.
Zlatan Ibrahimovic and Marco Verratti return from suspension for PSG but Thiago Silva joins Thiago Motta on the injury list while David Luiz is also a fitness doubt.
Blanc, who insists he is being realistic over his side’s chances of turning the tie around, said: “We have to think that we have to score and I am sure that we will but we have only a small chance to go through.
“We cannot afford to concede goals and that here is practically impossible. We have nothing to lose but will do our best.??
“All the teams that play here in Europe concede at least one. Barcelona have attacking players with incredible talent.
“We have to show that we want to win, show that we are capable of doing it and give a better account of ourselves than in the first match.”
But the Frenchman says the game may bring the best out of their talisman??Ibrahimovic, adding: “Ibra likes these kinds of games when there is nothing to lose.
“He will help us and I am looking forward to seeing him play. He is very important for us and is training hard each day.?? He is in good form.”