Pressure is on England to get Billy Vunipola (centre) fit and ready for the crunch match against France. Photo: AP Photo/Aaron Favila

TOKYO – England are awaiting the outcome of tests on Billy Vunipola's injured ankle as the number eight faces a race to be fit for their final Rugby World Cup Pool C clash against France on Saturday.

The 26-year-old started his 12th straight match, and seventh in two months, for England in Saturday's 39-10 victory over Argentina but left the field in pain at halftime after twisting his left ankle.

“We will have a clearer picture tomorrow. He's having a scan as a precaution,” England scrum coach Neal Hatley told a news conference on Monday.

“He's walking around with a smile on his face -- but it's nearly lunchtime so he's happy.”

Should Vunipola be unavailable, he could be replaced by Mark Wilson at number eight in Yokohama as Eddie Jones' side look to head into the quarter-finals with their 100% record intact.