GLOUCESTER'S Ben Morgan has been rated as a 'possible' to make Saturday’s massive win or bust clash with Australia in the Rugby World Cup at Twickenham.

But fellow number eight Billy Vunipola has been ruled out and has been replaced in the squad by Nick Easter.

Morgan is desperate to make the Pool A clash which could decide which side misses out on a quarter-final place after Wales’ shock victory over England last Saturday.

Morgan has a knee injury which forced him to miss the Wales defeat, while Vunipola came off midway through the match with a leg injury when arguably one of the most effective players on the pitch,

England head coach Stuart Lancaster also has fitness doubts over second row Courtney Lawes, scrum-half Ben Youngs and centre Jonathan Joseph.

The national coach said: “I would say 50-50 for Courtney and Ben Youngs, although with Ben maybe slightly better, so let's call it 60-40. It's very early still," Lancaster said.

"We're optimistic on Ben Morgan. With Joseph we are going to have to wait and see how he trains or if he can train on Tuesday.

"We want to give Joseph the best chance possible because if he was fit, he'd be a guy we want in the team."

Meanwhile, Morgan's Gloucester team-mate James Hook and Gareth Anscombe have been added to Wales' squad after Scott Williams and Hallam Amos were ruled out of the World Cup through injury.

Gloucester's Hook, 30, can play centre, fly-half or full-back and has won 78 caps, while Cardiff Blues fly-half or full-back Anscombe, 24, has one cap.

Full-back Liam Williams was concussed in the win over England in which Williams and Amos were injured.