Bundesliga side Mainz have submitted an €8m plus €2m bonuses bid for Metz defender Moussa Niakhaté, according to Le 10 Sport.
The 22-year-old started off his youth development as a left-back, but played as a centre back this season as Les Grenats tried to remain in Ligue 1.
The bid has not been accepted, and the clubs are continuing to talk.