PSG ran out comfortable winners in Piraeus back in September but the coach insists it was a tough night's work and is expecting it to be no different on Wednesday
Back in September Edinson Cavani opened the scoring but an equaliser from Vladimir Weiss saw the game remain at 1-1 until the final 22 minutes, before two Thiago Motta headers and a Marquinhos goal secured victory.
Les Parisiens are yet to taste defeat in any competition so far this season, but Blanc is wary of the threat posed by Wednesday's visitors.
"In the first game they tried to surprise us by pressing us in midfield and playing higher up, because they know that's where we are competitive," he told reporters.
"We must prepare to meet a side who will try to press us high up the pitch. But this could be a double-edged sword for Olympiakos because that will leave space in behind, which is good for us in terms of creating chances and scoring goals."
PSG left-back Maxwell was also quick to highlight the qualities of Olympiakos but stressed the improvement in Blanc's men since the opening weeks of the campaign.
The 32-year-old added: "Now things are different. We control games better. But Olympiakos have players of great quality and their coach Michel is well known in Spain. They can create problems but we must be confident at home."
PSG top Group C on 10 points ahead of the game, with Olympiakos three points further back in second spot.