Ranieri's side head to the Stade Geoffroy Guichard needing a win to keep pace with leaders Paris Saint-Germain at the top of the Ligue 1 table.
However, Monaco face a sizeable task if they are to take all three points against Christophe Galtier's team, who have lost only two home league matches this season.
"Eric Abidal has flu," Ranieri said. "I hope he can train tomorrow (Friday)."
"It will be very hard for us," he added. "Saint-Etienne caused us many problems in the first game, I remember it very well.
"Saint-Etienne have very good players on the flanks and a very strong, in-form attacker."
But, despite Ranieri's praise, Galtier believes Saint-Etienne will need to play at another level in order to take maximum points against the principality club.
Galtier said: "To beat Monaco you must be at 120 per cent and have success."
