The Ligue 1 giants head to Stamford Bridge on Wednesday needing a goal after the first leg of the UEFA Champions League last 16 tie finished 1-1 in France.
David Luiz said he knew what Mourinho would be telling his Chelsea team, which he left in June last year.
But the 27-year-old, who urged his team to believe they can advance, feels Mourinho's usual approach could be dangerous for the hosts.
"I know how Jose will prepare for this, he will be telling the boys to be patient and hit us on the counter-attack," David Luiz told The Mirror.
"He knows that we need to score and that they don’t, I know that is his way. We must be careful because I know that Chelsea have the ability to hurt on the counter-attack, but they must be careful as well.
"To sit back and just defend against Zlatan [Ibrahimovic], [Edinson] Cavani and [Ezequiel] Lavezzi can also be very dangerous, so it is not just us who have to be careful."
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