Vunipola, the 20-stone Saracens loosehead prop, is expected to make his first international start this weekend after seven appearances as a high-impact replacement.
The prospect of locking horns with Italian tighthead Martin Castrogiovanni holds no fears for Vunipola, and he said: "I am definitely ready."
He went on: "As a player you want to give the coaches confidence to give you a start. I am ready to do whatever job for the team against an experienced Italian team with Martin Castrogiovanni and Andrea Lo Cicero and a very strong pack.
"Castrogiovanni has been one of their big players. This is going to be a massive challenge, nearly as big as the French. We are going into it confident we can stick with them."
If Vunipola does replace Joe Marler, he will be tasked with shoring up an England scrum that came off second best against both Ireland and France.
Vunipola was fast tracked into the England squad for the QBE autumn internationals after just four Aviva Premiership starts for Saracens. The 22-year-old had been earmarked for international honours since his days as a dominant schoolboy at Millfield and in the England junior ranks.
In those days, Vunipola's appetite for rugby was only exceeded by his appetite but he went on a fitness drive after joining Saracens from Bristol in 2011. Vunipola arrived at the club "out of shape" but he has shed two stone. His brother Billy, the dynamic Wasps number eight who is on the fringes of national selection, has lost three stone.
"We'd starve ourselves by not having breakfast or lunch then come home and eat so much junk food," said Billy Vunipola, the younger brother who still tips the scales at 19st 12lb. "We would feast on whatever's quickest, the fastest food we could get our hands on: carbs, bread, potatoes, chocolates. And we'd eat a lot of it.
"Junk food is so cheap and those 'buy on get one free' deals didn't help us at all!"
tp://www.rfu.com (England's official website)
- Sports & Recreation
- Martin Castrogiovanni