Houllier said: "I think there could be as many as six teams involved in the battle for fourth place.
"We have to be careful what is going on behind us as well as what is happening ahead of us. Blackburn, for example, could go on a good run.
"I think it is going to go right down to the final week. It will be exciting but we know what we have to do and we will give it our best shot."