Claudio Ranieri's side go into the home tie third in the French top flight, having won just one of their last four fixtures.
An impressive triumph at surprise-package Nantes last time out arrested their slump, leaving them five points behind leaders and champions Paris Saint-Germain.
Monaco have won five and drawn two of their seven home games this term, while Falcao has netted nine goals in 14 games since a reported €60million switch from Atletico Madrid.
However, after a goal-laden start to life in France, Falcao has scored just twice in his last seven outings and Ranieri hopes the Colombia international can return refreshed after a spell on the sidelines.
The Italian said: "During the last game (against Nantes), he had a problem. So we don't want to take any risks against Rennes.
"I hope he will be ready against Nice next week.
"Obviously it will be more difficult (without Falcao). He is our top scorer. But I hope that he will be motivated when he returns.
"And against Rennes, the whole team should work harder without him."
Emmanuel Riviere is likely to replace Falcao in Monaco's attack. The 23-year-old has six goals to his name from 10 games this season.
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