Toon face a difficult task in Portugal tonight.
"Mission impossible? There is never a mission impossible," Pardew said. "But we know it is a tough ask. And we know we can get a result. We need to give ourselves a chance for Thursday week and the return at St James' Park.
"It's a big test for us because I think when you play a team who are such a roll as Benfica are, it's always difficult. They have great momentum and that confidence breeds it's own success. It's a difficult game for us, we're under no illusions about that."