Eddie Jones joked the best way to keep Billy Vunipola fully fit is to keep him away from Kobe beef after naming the number eight in England's side to face the United States in the Rugby World Cup.

Vunipola started in England's 35-3 victory over Tonga on Sunday and was the recipient of some tough tackling from the islanders, who his father had previously captained in the World Cup.

Jones has made 10 changes to England's side for the USA encounter in Kobe on Thursday, though despite the hits he took against Tonga, Vunipola is one of the five players to retain their place.

However, Jones has no concerns over Vunipola's fitness, as long as he can keep the 26-year-old on the field, rather than risking him tucking into Kobe's famous delicacy.

"He loves playing, the best way to keep him fit is to play him and he's an influential player in our team," Jones told a news conference on Tuesday.

"There's a risk him going out and eating Kobe beef tonight, so we feel it's much better he plays rugby than goes out to eat beef.

"We've got a squad of 31. We've got a plan for each player. Some players need to play a lot of rugby and some players are better every so often.

"We've tried to manage the squad in terms of injuries. We've tried to manage them in terms of what we need for each game to ensure we get the desired result."

Vunipola's older brother Mako is also in the squad, though is yet to feature due to injury, with Jones confirming the Saracens man should be available for the contest against Argentina on October 5.

"Mako is still a little while away, he should be available, as should Jack Nowell, for the Argentina game," Jones added.

"[Henry Slade] got a bit of a knock on his knee and we decided not to risk him, we want him right for the next game."

Despite flashes of excellence, mainly from Manu Tuilagi, England struggled to hit their highest level against Tonga, and Jones is confident his side will click up another gear against the USA.

"We're ready for the next step. Looking forward to the USA, they'll be a different proposition, they've had two weeks to prepare for the game," he said.

"We know they've been down in Okinawa training with the marines and they'll be ready for the battle.

"Our aim now is to be a bit tidier in attack, we'd like to execute a little bit better. There was a lot of effort in our game on Sunday but not the execution so we're looking to execute better in attack and be a bit more physical in defence."