Olympique de Marseille forward André-Pierre Gignac faces an as yet undetermined spell on the sidelines after breaking a bone in his left foot.

Gignac limped off 20 minutes into OM's 1-0 defeat at ES Troyes AC on Sunday, a result which knocked them off the top of Ligue 1. The first medical checks revealed a fractured fifth metatarsal bone in the 26-year-old's left foot, which will keep him out for weeks or even months. "It's a blow," coach Élie Baup said. "We don"t know exactly how long he will be sidelined."

Following two seasons marred by various injuries, the French international has been in top form this season, scoring eight goals in all competitions, including both in the 2-2 draw with Paris Saint-Germain FC on 7 October. "I'll be back stronger, I'm a winner," Gignac promised on Twitter.

Marseille play VfL Borussia Mönchengladbach on Thursday in UEFA Europa League Group C.