England expect to be without Billy Vunipola for the entire NatWest 6 Nations in a development that sees Zach Mercer shed his status as apprentice player.

Eddie Jones has all but ruled Vunipola out of the quest for a third successive Championship crown due to the fractured arm sustained on European duty for Saracens last weekend, his fourth major injury inside 14 months.

Further thinning England’s resources in the position is the knee problem that prevents Nathan Hughes from taking part until the latter rounds, leaving Mercer and Sam Simmonds to battle it for the vacancy in the back row.

England head coach Eddie Jones is preparing for the Six Nations
England head coach Eddie Jones is preparing for the Six Nations (Steve Parsons/PA)

“We’ll get Nathan Hughes back halfway through, possibly. He’s probably rehabbing a little bit slower than than we first thought. I don’t think we’ll see Billy,” Jones said.

The losses at number eight mean Mercer has been elevated from apprentice to full-blown contender to start the Six Nations opener against Italy on February 4.

Jones used the term to describe Mercer when picking him and Marcus Smith in England’s training squads late last year, handing them learning briefs rather than viewing them as genuine options for inclusion in a matchday 23.

Smith is still regarded as a long-term prospect, but 20-year-old Mercer’s improvement for Bath in recent months has caught the eye of England’s management.

“The situation means he’s got a shorter apprenticeship than was first envisaged,” Jones said.

“He’s now fully available for selection. He’s done well for Bath and I’ve been really impressed by his work-rate off the ball.

“There’s a certain hardness about his game. He’s always been one of those gifted boys but now he’s doing the tough things.

“I’ve been really impressed and he could certainly get an opportunity during the Six Nations.

“He’s done one hell of a lot in the period that we’ve picked him from November until now.

“He has a nice, natural skill set that enabled him to be selected in the first place and now it’s a matter of his hard work, his attitude and willingness to do the things that hurt.”

Harlequins’ Marcus Smith is rated highly
Harlequins’ Marcus Smith is rated highly (Mike Egerton/PA)

Jones has named eight uncapped players in a 35-man squad that will travel to Portugal on Sunday for a week-long training camp due to the host of suspensions and injuries that has robbed them of 13 players.

Saracens wing Nathan Earle, Northampton centre Harry Mallinder and Harlequins full-back Marcus Smith are the rookie backs included.

Exeter prop Alec Hepburn, Harlequins prop Lewis Boyce, Newcastle flanker Gary Graham, Bath back row Zach Mercer and Bath hooker Tom Dunn make up the new faces in the forwards.

England have been installed as favourites to win the Six Nation, but Jones looked for enemies when asked if the squad selected on Thursday was good enough to deliver the title.

“If you read the papers, then we might as well not turn up. I don’t even know why we’re having this press conference,” Jones said.

“Ireland are dominating Europe, their sides are going well. They have this central contracting system that allows them to have their players at their peak.

“As you’ve seen, we’ve got 13 players out. So we’ve got no hope.”