Former England fly-half Rob Andrew says Andy Farrell has a golden chance to prove his worth in Friday's World Cup Pool A game against South Africa.
Farrell came on as a replacement centre against USA in Lens
The Saracens player will start as England's first-choice goalkicker, and will share the responsibility of playing at fly-half with Mike Catt.
"It's a wonderful opportunity to prove what a great player he is," said RFU elite rugby director Andrew.
"If any man had a chance to show what he's made of, Andy has his on Friday."
Andrew admitted England were in an awkward situation after losing their fly-halves Jonny Wilkinson and Barkley to injury and skipper Phil Vickery to suspension.
But Andrew, a former England stand-off, said he is confident that coach Brian Ashton's men are up to the task.
"It is not just a challenge for Andy, it is one of the biggest challenges this group of players will ever have faced," he said.
"I, for one, believe they will respond. It is a bit of backs-to-the-wall stuff."
Former Wigan star Farrell captained Great Britain at rugby league before switching codes in March 2005.
I would imagine two-point pressure kicks are exactly the same as three-point ones
RFU elite rugby director Rob Andrew
His early rugby union career was plagued by injury but since recovering fitness he has settled at centre after a brief experiment at back-row.
"Andy has shown all along that he's got all the attributes in terms of his skills and his decision-making, his kicking and defence," Andrew said.
"In terms of the goal-kicking, Andy has kicked many pressure points in rugby league, and I would imagine two-point pressure kicks are exactly the same as three-point ones.
"You've all questioned his pace but there have been plenty of fly-halves who have played who don't have great pace.
"We are beginning to see in the warm-up games and in glimpses at the weekend the sort of qualities people have seen in Andy Farrell over the last few years and the reasons he was brought across to rugby union.
"The issue is that he lost his first year of preparation in union through injury and has been playing catch-up ever since."
Farrell will line up alongside the veteran centre Mike Catt, 35, who has plenty of experience at fly-half.
"We all know how the modern game revolves around the 10-12 area and I'm sure they are not going to stay in those positions the whole time," Andrew added.