Houllier said: "In Europe there are no more big scores, that's finished! There's no easy games in Europe any more and the early rounds are always difficult. It is a lack of respect to the opposition if you say we are going to win.
"In the last three years, Chelsea have gone out to a Swiss team, an Israeli side and, last year, a Norwegian team. So nothing is straightforward.
"Sometimes you have to go to difficult grounds, face hostile crowds and play on pitches which are not the best. You have to show how big and professional you are.
"We have had a good luck at Olimpija both home and away, and we will be prepared for it in the right way. We have prepared for this game exactly as we would if we were playing Barcelona.
"I've always said the first leg of a two match European tie is always the most difficult and we want to do our best and take a good result back to Anfield. The pitch is not the best but we will adapt."