Raymond Domenech is remaining cautiously optimistic over William Gallas' recovery from a calf injury.
Gallas has been included in France's provisional squad for the World Cup despite missing the end of Arsenal's season after aggravating the problem against Barcelona in the UEFA Champions League.
He may not be risked when Les Bleus face Costa Rica in a friendly on Wednesday and Domenech is not totally convinced there will be no setbacks.
However, he has been encouraged by Gallas' progress in training and hopes the defender will be ready for the opening game against Uruguay.
"There is always the uncertainty with Gallas," said Domenech. "We can be optimistic from what we have seen in training, but that is not the same as in a game.
"We do not know if he will be okay for Costa Rica.
"It does not hurt now, but we must be careful with the calf. We want it to be ready for the World Cup."
Gallas gave Domenech a fresh scare on Sunday when he rolled over while taking part in a dune buggy race at the team's training camp in the French Alps.
But he escaped with just a graze on his left hand and fellow defenders Gael Clichy and Sebastien Squillaci are confident Gallas will be fit for the tournament.
"William is our main man at the back and we need him," said Clichy, who plays alongside Gallas at Arsenal.
"I have no doubt he will play at the World Cup. He has hiked up with us in the snow and has been training with no problems.
"I know him well, he's strong, he won't give up and he will make the trip with us."
Squillaci added: "From what I see, he's physically fit and he will stay with us until the end."