Sinfield backs injured France captain Dupont to make swift return
Former World Rugby player of the year Dupont left the field in pain during Thursday's 96-0 win over Namibia after a clash of heads but the French federation says he is staying with the squad while he undergoes further checks.
"I'm disappointed for the competition at this moment in time but we have no doubt he'll be back," Sinfield told reporters.
"World-class players like that get themselves right very quickly and I'm sure he's doing everything he can.
"We've seen players before play with facial fractures and I suspect he will be back on his feet and available very soon," he added.
France attack coach Laurent Labit said on Friday the team will wait up to 72 hours, after Dupont sees a specialist, to announce whether the 26-year-old will be able to continue in the tournament.
Dupont scored a try and provided two sublime kick-assists in the victory over Namibia as Les Bleus continued their unbeaten start to the competition, underlining their status as favourites on home soil.
"I saw the way they played last night, with him fizzing around, he's pretty special," England scrum-half Danny Care told reporters.
"For the World Cup you want to see the best, Antoine's the best player in the world.
"We want to see him back in a French shirt," he added.