Houllier said: "I noticed that Diouf has come off early in seven of our last eight fixtures. Against Bucharest he was booked and I had to bring him off to protect him from a possible red card.
"He has only played one full 90 minutes in the past six weeks so I wanted him to play tonight to build his fitness and sharpness.
"Anthony Le Tallec and Bruno Cheyrou will also play, but I will not risk Pongolle because we are so short of strikers at present."