Saracens and England star Billy Vunipola is “gutted” that his World Cup campaign is over after his injury in Saturday night’s painful defeat to Wales.

But he says he will be giving his all for England from the stands as the host nation fight to ensure they do not also suffer an early exit in the group stage.

Vunipola, who impressed in the number eight role against Wales, hurt his knee as England threw away a 10-point lead to lose 28-25 at Twickenham – and he faces four to six weeks out of action.

He tweeted: “I’m gutted to say that my 2015 [World Cup] journey has come to an abrupt end. Now time to give my all for [England] from the stands.

“[I’m] humbled by all the messages and support and thank you one and all. I’ll be back, but for now let’s bring the noise [Saturday].”

England lie behind Wales and Australia in Pool A and, with only two teams going through to the knockout stages, Saturday night’s showdown with the Aussies is now a make-or-break clash.

Saracens and England scrum-half Richard Wigglesworth said: “Fair play to Wales, they got desperate and it worked for them.

“Unfortunately it’s done now and, however frustrating it is, we’ve got to try to beat Australia – and the only way to do that is to get on the front foot, rip in and see where it leaves us.”