France's talisman and captain Antoine Dupont was set to undergo new tests on Friday after suffering a facial fracture in the win against Namibia that has jolted the host nation's hopes of winning the Rugby World Cup for the first time.
Dupont, 26, will almost certainly miss France's final pool game against Italy on 6 October and could be a doubt for a potential quarter-final against reigning champions South Africa or Ireland, the world's number-one-ranked team.
The French federation said the scrum-half had suffered a "maxillo-zygomatic fracture", meaning a facial injury.
"Specialised surgical advice was requested to assess how long he will be unavailable for," the federation added, but it said Dupont would remain with the squad.
Later, the president of Dupont's club Toulouse, Didier Lacroix, said Dupont would travel to the southwestern city for "additional scans".
One of France's most eminent facial surgeons will also examine Dupont "to define the best way forward, either an operation or not. First of all, we have to be 'secure' about the player's safety," Lacroix said.
France's assistant coach Laurent Labit said: "We're waiting for the specialist's opinion... we'll wait 48 or 72 hours to see where we really are."
Dupont left the field visibly in pain in the 46th minute of Thursday's 96-0 rout following a clash of heads with Namibia captain Johan Deysel.
Deysel, who was initially handed a yellow card that was later upgraded to a red, apologised on Friday.
"I would like to extend my best wishes to Antoine Dupont. Clearly, I meant no harm. Everything happened very quickly and I couldn’t get my head out of the way quick enough, resulting in a head clash," he said.
The importance of Dupont, a former World Rugby player of the year, is underlined by the fact that he is yet to lose in a France team he has skippered on home soil in 14 Tests.
VICTORY, BUT NO PARTY
France scored a national record 14 tries in their third consecutive win in the tournament but prop Cyril Baille said Dupont's injury had completely overshadowed the performance.
"We know how important he is in the squad, what he brings," said Baille. "It tarnished the evening somewhat, there's a lot of stress.
"Of course, we're happy with the scoreline, but it wasn't a party in the changing room after that."
Flanker Francois Cros, who like Baille is a teammate of Dupont at Toulouse, said that if the injury turned out to be serious, "it would obviously have an impact on him and on us".
Cros added: "We still have some experienced nines who can take over."
Lyon's Baptiste Couilloud came on for Dupont and was full of running as he scored a try of his own, as he ensured the French team re-discovered their rhythm after a raft of replacements.
The third scrum-half in the 33-man squad is Bordeaux-Begles' Maxime Lucu, who won the man-of-the-match award in the second pool victory against Uruguay.
Head coach Fabien Galthie faced questions after the match about whether Dupont should have been replaced at half-time of a game France were clearly going to win.
"What do you want me to say? You can't take 14 players off at half-time. Our plan was to bring off one, three and five at half-time, then the rest at the 55th minute," he said.
"The aim was to give everyone some game-time and not sit back for a month. The players wanted and needed to play."
There was sympathy for Dupont from other countries. England defence coach Kevin Sinfield said: "We have no doubt he'll be back. World-class players like that get themselves right very quickly and I'm sure he's doing everything he can."
France are already without their first-choice fly-half, Romain Ntamack, who was ruled out of the tournament with a knee injury.