Arsenal's young defender William Saliba has suffered a broken foot while on loan at Saint-Etienne.
The 18-year-old broke his fifth metatarsal in Les Verts' 1-0 victory over Monaco on Sunday night, his second notable injury of the current season.
Saliba, who signed for Arsenal in the summer for £27m before returning to France on a season-long loan, missed the opening few weeks of the campaign with an adductor muscle problem.
Saint-Etienne confirmed the news in an official statement, saying: "William Saliba, victim of an injury against Monaco last Sunday, suffered a crack in his fifth metatarsal and will miss the confrontation against Oleksandriya in the Europa League."
The French youth international is expected to be out for weeks rather than months, news which will somewhat soften the blow to Claude Puel's side, who have looked highly organised since he came into the team at the end of September.
