Tokyo - England coach Eddie Jones on Saturday said number eight Billy Vunipola's ankle injury wasn't thought to be serious after he withdrew in discomfort from the Rugby World Cup win over Argentina.

Vunipola was substituted at half-time in England's 39-10 rout of 14-man Argentina, sparking fears for the fitness of a player who has become a talisman for the side.

Jones tried to laugh off the injury, telling reporters twice that Vunipola had "slipped on a piece of Kobe beef".

But when pressed, Jones revealed: "He's twisted his ankle but we don't think it's too serious."

Vunipola has been injury-prone throughout his career and had to pull out of the 2017 British and Irish Lions tour after shoulder surgery. He has also had problems with his knees, and twice broken his arm.

On the other hand, Jones said it was a "real plus" to welcome back from injury Vunipola's brother, prop Mako Vunipola, and winger Jack Nowell who scored a spectacular late try.

"We had two guys, Mako and Jack Nowell, who haven't played rugby for five or six months at least and they got a bit of a gallop. Jack scored a try, Mako scrummed well and took the ball forward well. So there's real pluses there for us today," said the Australian coach.

The bonus-point win means England are the first team to qualify for the quarter-final stages and they will play France in their last Pool C encounter, possibly to decide who tops the group.

"After three games with 15 points, we'd be pretty happy," said Jones.