Mario Balotelli will miss Nice's next three games after sustaining an injury in shooting practice.
The Italian arrived in France on a free transfer on deadline day, and a move to the Cote d'Azur appears to have reinvigorated the former Manchester City, Liverpool and AC Milan striker.
He has seven goals to his name for Nice, with six coming in the league - with those efforts helping the club to the top of the Ligue 1 table.
But they will now have to cope without their talisman for the upcoming fixtures with Bastia, Toulouse and Guingamp.
The ailment also forced Balotelli to miss Thursday's 2-0 defeat to Schalke, which saw Lucien Favre's men knocked out of the Europa League at the group stage.
"He won't be available for the three matches to come over the next 10 days, that's for sure," said Favre.
"For the matches that come after that, we don't know yet."
Nice will also be without defender Paul Baysse for the rest of the year because of a knee tendon complaint.
Going into Sunday's meeting with Bastia, Nice hold a three-point lead over Monaco and Paris Saint-Germain at the top. They have not won Ligue 1 since 1959.