Lorient, the surprise contenders in Ligue 1, on Monday said they had lost captain Laurent Abergel until after the World Cup with a broken arm.
Abergel suffered the injury in Sunday as Lorient won 2-1 at Breton rivals Brest to climb to second in the French top flight, one point behind Paris Saint-Germain after ten matches.
Abergel set up the first of his team's two goals.
The 29-year-old midfielder will miss Lorient's next five games, all in the league and including the visit of PSG on 6 November.
He should make his return when the league resumes on 28 December after the World Cup.
"This injury is nothing compared to the strength of this team. I will give everything for this squad in another role and come back as soon as possible even stronger," Abergel wrote on Instagram.