Beppu - England star Billy Vunipola is "very likely" to be available for their Rugby World Cup quarter-final against Australia, according to defence coach John Mitchell.

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The powerhouse number eight has been a doubt for Saturday's crunch match in Oita ever since going off with an ankle injury at half-time during England's 39-10 win over Argentina 10 days ago.

England coach Eddie Jones will name a team to play his native Australia on Saturday, with Vunipola sure to be included if fit given the Saracens back-row is the only player to have started all 12 of England's Tests this year.

"Billy is progressing really well," Mitchell told reporters at England's hotel on Tuesday.

"He has trained again today and we are very confident in his progression each day. He's very likely (to be available).

"Billy is a very important player to us and a very likeable player as well. He fits well within the team.

"He loves the ball in his hand. He is very good at regaining and retaining momentum. He likes carrying the ball which is where he has his greatest influence."

However, it's looking far less likely that Jack Nowell will feature against the Wallabies this weekend.

The wing made a comeback against the Pumas after recovering from ankle surgery and being forced to have his appendix removed, only to then suffer a hamstring injury that prevented him from taking a full part in training on Tuesday.

"Jack wasn't at training today. He is on another prescription of training and is also progressing," Mitchell said.