Kylian Mbappe limped out of training just four days before France's opening World Cup game against Australia in Kazan.
The 19-year-old forward appeared to hurt his left ankle in a tackle from defender Adil Rami during a practice match on Tuesday.
Mbappe, who is expected to be a starter in Russia, received treatment from support staff and attempted to play on before leaving the session, placing him in doubt for Saturday's clash with the Socceroos.
Didier Deschamps will hope the knock is only a minor concern after losing both Laurent Koscielny and Dimitri Payet to injury prior to selection of the final 23.
France's other Group C opponents are Denmark and Peru.