Houllier said: "Cisse will have a major impact here. He is quicker than Henry.
"He does not have the same skill as Henry but that will come. It will take a bit of time because it is a different game here strong and powerful.
"For the third season in a row he is the top scorer in France with more than 30 goals. I have been following him for three seasons now and Cisse and Michael playing together - that is an exciting prospect.
"There will be some pace there and I think Michael will get even better. His game has changed a bit and he is more mature in some aspects of his game."