The Blues were beaten 3-1 by the French champions at Parc des Princes last week but that has not dampened Mourinho's spirits as his side prepares for the Stamford Bridge visit of Laurent Blanc's men.
"I believe and my players believe. That's the most important thing," said Mourinho.
"I think if Paris is knocked out it will be a big disappointment for them; if we are knocked out it's something that, in this moment, lots of people are expecting.
"We have to enjoy the risk of the situation. At 9.30 we can be out and we know that we have this risk. But at 7.45 we have chances to be in the semi-final.
"We have to be at 7.45 with a smile on our faces, go in, play, give everything. At 9.30, let's see what happens. But at 7.45 we believe that we can do it.
"I think we are going to win, really. In the end of the two legs, I think we are going to score more goals than them.
"In this moment it's 3-1, I think in the end it can be 4-3 or 5-4. If I don't think that way I don't go on Tuesday. And I go and I'm happy to go."
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