The club's £11.5 million record signing missed Saturday's 2-0 win at West Ham United with injury and it has been found he has suffered a fractured leg.
The former Lyon ace, who has failed to find the net since moving to Craven Cottage, picked up the knock in last week's win over Southampton.
Assistant manager Christian Damiano confirmed that Marlet will be missing until the New Year at least.
"Steve has a hairline fracture just below his knee and will be out for two months," said Damiano.
