France coach Didier Deschamps said Lucas Hernandez's knee injury "seemed pretty serious" after the Bayern Munich defender hobbled off in the holders' World Cup win over Australia on Tuesday.

Deschamps' men, bidding to become the first team to successfully defend the title since Brazil in 1962, had already seen Karim Benzema, Paul Pogba, N'Golo Kante and Presnel Kimpembe ruled out before the tournament.

"He's going to do some tests, it seems pretty serious to me," Deschamps told French broadcaster TF1.

"We'll have to confirm anyway. That's the big black spot for tonight."

France had to come from behind after Craig Goodwin's ninth-minute opener for the Socceroos.

Olivier Giroud scored twice to draw level with Thierry Henry on France's all-time scoring list, with Adrien Rabiot and Kylian Mbappe also on the scoresheet in a 4-1 win.

"Even though we were caught cold at the start, we did everything right afterwards," added Deschamps.

"In the second half we could have had an even bigger winning margin, but we did a lot of good things."