Monaco defender Sylvain Monsoreau has been ruled out of action for up to five weeks due to injury.
The summer signing from Lyon strained a thigh muscle in the Ligue 1 tie with Nantes and was immediately ruled out of Saturday's derby against Nice.
Monsoreau will now undergo an MRI scan in order to assess the full extent of the blow, but the Principality side are readying themselves for the news that the left-footed ace could be absent for over a month.
Both Mohammed Kallon and Sebastien Grax are still continuing their comebacks from lengthy injuries and will also miss the Cote d'Azur derby, with caretaker coach Laurent Banide in desperate need of a win.
ASM are currently rock bottom of Ligue 1 and another bad result against Nice is likely to fuel talk that Banide is viewed merely as a temporary fix.
The 2004 UEFA Champions League finalists have been linked with Internacional boss Abel Braga, with the latest reports indicating that Monaco have offered the former Marseille manager a substantial financial incentive to return to France from Brazil.