"They are definitely the toughest opponents we've had in a qualifier," Carragher told the club's official website.
"I know people expect us to get through, but it's not as if we're playing a Mickey Mouse team.
"The Belgian league has a lot of quality and their champions are used to getting into the group stages.
"We had a tough match against Anderlecht a few years ago, so I'm not surprised Liege caused us problems.
"We didn't play well and we know we'll have to improve at Anfield. Everyone knows how important it is for our season to get into the group stage.
"You have to bear in mind this is probably the biggest game of the season already, and in some cases it may be the most important match they've ever had in their career.
"It would be unthinkable for us not to be in the Champions League. You just want to get this qualifier out the way, put Europe on the back-burner for a while and get focused for a couple of months on doing well in the league.
"As players we expect to be there and so do the fans. We know in this situation all the pressure is on us, but we don't want to get negative about that."