The number eight was withdrawn at half-time in the crushing 39-10 win over Argentina after feeling a "twinge".

Mark Wilson is primed to replace Vunipola against France on Saturday.

"If it's not right for him to play, then we have a squad of 31 and we have really good players in that position," assistant coach Neal Hatley said.

"Billy is getting looked at today and we will have a much clearer picture tomorrow [Tuesday]."

Vunipola has started all of England's recent games, with head coach Eddie Jones insisting he benefits from game-time rather than being rotated.

"It's a little bump [on the ankle]," Hatley added.

"He's walking around and is in good spirits. We'll give it time to settle and will plan appropriately.

"It's not worth risking anyone. Tom Curry has slotted in at eight. [Mark] Wilson played the whole of the autumn for us and did a really good job."

Meanwhile, captain Owen Farrell is showing no delayed ill-effects after being smashed high by Argentina lock Tomas Lavanini, who was sent off for the dangerous challenge and has since been banned for four matches.

Farrell trained fully on Monday in Tokyo and is set to again lead the side against the French in the Pool C decider in Yokohama.

Prop Joe Marler is being monitored with a minor back niggle.