Tokyo - England key man Billy Vunipola has had a "precautionary" scan on his injured ankle but is walking normally, according to coach Neal Hatley, adding that a full diagnosis wasn't expected until Tuesday.

The number eight, an integral part of England's plans for winning a second World Cup, was substituted at half-time during England's 39-10 win against Argentina on Saturday.

Head coach Eddie Jones had initially tried to shrug off the injury, saying Vunipola "slipped on a piece of Kobe beef". He eventually admitted he had twisted his ankle, adding that it was not "too serious".

Hatley revealed Vunipola had had his ankle scanned "as a precaution" and was spending time with the physios.

"He's busy being assessed and that will go on throughout the day and we'll see how he pulls up tomorrow," Hatley told reporters on Monday, with a firm diagnosis expected in the next 24 hours.

"He's around, walking around, big smile on his face. It's nearly lunchtime, so he's pretty happy. But he's all good," joked the coach.

Hatley said there were plenty of players in England's pack who could compensate for Vunipola's carrying ability if the number eight is ruled out.

"You plan for all eventualities. With what we've got with Ellis Genge and Mako (Vunipola), Kyle Sinckler, Maro Itoje, Courtney Lawes. People pick up the slack like you have to," he said.

He noted that England had been forced to play a lot of rugby without both of the Vunipola brothers and other players had stepped up.

Hooker Jamie George added that Jones had told the other forwards to carry more when Vunipola came off against Argentina.

"Whenever they see me or Billy as an option, Willi just passes to Billy, which is probably fair enough," he said, referring to scrum-half Willi Heinz.

"If he does or he doesn't play, we're all aware that we need to make sure we get our hands on the ball and impose ourselves physically on the game," said George.

England, who have already qualified for the quarter-finals, play France on Saturday to decide who tops Pool C.