Dortmund, who cut the gap to two points with a 1-0 victory at Bayern last weekend, will be without holding midfielder Sven Bender after he broke his jaw in the 2-1 defeat by Arsenal in the Champions League on Wednesday.
Playmaker Mario Gotze could also miss the meeting of the Ruhr valley rivals after picking up a knock just above the knee against Arsenal.
"Dortmund will be without Bender until January," the club said on Thursday after the 22-year-old underwent a three-hour operation in London.
"Gotze's derby participation is also in doubt [but] the medical staff are hoping he can be fit for Saturday."
Germany international Gotze has led Dortmund's recent revival and scored the winning goal against Bayern.
"Beating Dortmund would be a major boost for us," said Schalke midfielder Lewis Holtby. "They played well in Munich last week but the mother of all derbys in Germany is a different story."
