Hugo Lloris fears Lucas Hernandez has suffered an "important injury", dealing France yet another blow as they bid to defend their World Cup crown.
And left-back Hernandez was added to that injury list after he went down in attempting to stop Matthew Leckie's cross for Australia's shock opener.
The outlook does not look positive for the Bayern Munich defender, but France captain Lloris hopes his team-mates can rally as they have done before.
"It's never good to see one of your team-mates leaving the field in that way," he said. "I believe it's an important injury.
"He's not the first one, but we have to continue to look forward. Unfortunately we could not count on him, but we have a team with other players that we trust.
"We have to stay together and keep believing, keep our focus on that."
Lloris added: "We have important players left on the side for injuries, but luckily we have a lot of talented players in France, players we can trust, because they have the talent, the mentality and the desire to perform at the highest level.
"We try to create something special inside the team day by day. We try to enjoy the moment, not only on the pitch but also off the pitch.
"We have to take it game by game. Obviously it's a World Cup, there's no easy games and we have to be ready to face difficulties. When we face difficulties, we have to make sure that everybody raises their level."
The previous three holders have exited the World Cup at the group stage, but that sequence appears unlikely to be extended now.
Indeed, France's 4-1 win was the biggest in the first game of a title defence in World Cup history.
"We're obviously pleased with the result and pleased with the performance," Lloris said.
"I believe we had a good start in that game, but unfortunately we conceded that goal. We also lost one of our team-mates in this action by injury.
"But the team stayed calm, and we took control of the game and slowly started to dominate and created chances, then we scored one and two.
"Second half, I think we controlled perfectly. It's a good start."