Billy Vunipola says he has reached only 50 per cent of his full potential as he and England aim to turn recent success into world domination.
Vunipola was an instrumental part of England's historic 3-0 series win in Australia last month but, like Eddie Jones' resurgent side, he is far from finished yet.
The 23-year-old has enjoyed the best season of his career so far, winning 10 out of 12 international Tests, which included three man-of-the-match awards en route to a Six Nations Grand Slam. He also won the Premiership and Champions Cup with Saracens.
Jones, however, has challenged Vunipola to become the finest number eight in the world and, asked to put a figure on his progress, the 23-year-old was clear.
"I'd say I'm 50 per cent," Vunipola told Press Association Sport.
"I can add another 50 definitely. There's a lot left. I feel like I can get way better than I am at the moment.
"I want to be the best. I was too scared to say it because I'm not anywhere near that level yet but Eddie laid down the challenge and it's there on paper now.
"I don't want to be an average rugby player. I don't want to be just a good Premiership player, who was OK at international level. I want to be very, very good at both."
Key to that, Vunipola says, will be continuing a physical transformation, which has seen the 126kg forward curb his love of junk food and adopt a more disciplined approach.
"It's about having that awareness of my own fitness, I've matured in that way," Vunipola said.
"It's not a matter of never eating badly, you have to feed your soul as well as your body. If you're always on a diet you end up being miserable."
England are rejuvenated too, their whitewash Down Under taking them to number two in the world and 10 matches unbeaten this year.
Victories against South Africa, Argentina, Fiji and Australia in the autumn would represent a record-equalling 14 wins in a row.
"It's more important for us to catch the All Blacks," Vunipola said.
"It's important we don't start chasing wins. Once you start thinking about 14 wins you start losing focus of the things that got you there.
"You put a lot of pressure, unnecessary pressure, on yourselves to perform."
New Zealand are the target and if the world champions have shown anything over the last decade, it is that domination can only be earned over time.
"It's inevitable we're going to have a dip at some point, that's human nature, but it's important then that we stay close as a group and don't get drawn into over-reactions," Vunipola said.
"The All Blacks have lost games but they never over-react. They stay true to themselves and they've stayed at that level for such a long period. It's not one or two years but eight, nine, 10 years.
"That's what we're pushing towards. It's a big challenge but one we're excited to face."
It is almost a year since England's humiliating World Cup campaign began and the turnaround since has been as quick as it has been remarkable.
Even as they celebrated their third and final victory against Australia, Jones was reminding his players of the next hurdle to jump.
"With Eddie there's always a bigger and better challenge," Vunipola said.
"That's the best thing about him. He pushes us to be better, he believes we can be better even when we didn't believe it.
"After the last match he said, 'congratulations, have fun tonight', but he was also clear, he said, 'this isn't the end, know there's a bigger goal to go after'.
"That's what he's about and we are too. We don't want to be just contenders, we want to be number one in the world. That's the goal now."
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Source: PA
