"There's only one team which has beaten them by two clear goals, and that's Barcelona," Pardew told reporters. "So that's the size of the task, so we are under no illusions there.
"This is a Champions League team, really, and if it weren't for Celtic's fantastic performance in the group, they could have been competing in the Champions League.
"That's the quality we are up against. I don't think there are going to be many better sides that have played here than Benfica."
Newcastle will need to win by three goals if Jorge Jesus's men score two or more at St James' Park.