The Spaniard is struggling with a hamstring injury and will miss the trip to Stamford Bridge.
Wenger said: “Fabregas is not fit to play in this one and nor is (Manuel) Almunia.”
Wenger also revealed that Kieron Gibbs will be out of action for up to three weeks.
Gibbs sustained a calf injury in the win over Partizan Belgrade in the Champions League on Tuesday.
Wenger added: “We lost Gibbs as well on Tuesday night with a calf problem and he is out of the England squad as well. He is out for two to three weeks.”