Sir Clive Woodward believes England have lost out in not tempting Sam Tomkins to change codes from rugby league to rugby union.
While Tomkins' brother Joel makes his debut for England against Australia on Saturday at Twickenham, the World Cup-winning coach claims Sam could have made a big impact on the 15-man code.
The elder of the two brothers, Sam became the most expensive player in league history when he signed for New Zealand Warriors from Wigan at the end of the Super League season.
But with younger sibling Joel lining up in the number 13 jersey this weekend, Woodward is adamant that Sam could have solved some of England's midfield problems.
"Outside centre is the one big question mark for this generation of England players. Sam Tomkins was born to play 13 for England and we should never have allowed him to leave the country to play rugby league in New Zealand," Woodward wrote in the Daily Mail.
Woodward maintains that none of the current members of England's backline would rank in the top three in their position in world rugby.
"Imagine an Olympic podium consisting of the top three players in the world for each position in rugby," added Woodward.
"I do not believe there is a player in the England back line who would be on that podium on current form, but to win the World Cup they need to find at least two outright gold medal winners by selecting players with gold-medal potential. They are definitely out there, and the England team should be built around them.
"I realised (when I was England coach) that if you had a gold-medal contender in every position on the pitch, and on top of that world-class coaches, you would have every chance of becoming the best team in the world.
"To that point, I made it the players' individual responsibility to become the best in the world in their position. I dedicated myself to providing them with everything they needed by way of coaches, sports science and world-class facilities but made it clear that we did have the talent, but they had to leverage that talent by working harder and better than anybody else.
"I told Jonny Wilkinson that, at 18, he was the best fly-half in England, but I would rank him sixth in the world. That's not even on the podium - I wanted him to be number one in the world.
"In the years that followed, the players' response and dedication to achieving this was inspiring and six years later, in my mind, every player in the team that started the 2003 World Cup final had a place on that Olympic podium. I believe seven were gold medal winners, five were silver and three were bronze."