Jones has already made some bold selection calls, bringing Joe Marler out of retirement and axing the experience of Mike Brown, Chris Robshaw and Danny Care.

"Selection is harsh," Jones said.

"It is always about picking the best player at that particular time."

Jones told BBC Sport that big names left out "are not out of the picture", but that the latest 38-man training squad picked itself.

"Of course it is tough. They have been good competitors for England and they still have more to give," he said.

"Players generally select themselves. I was taught that by [former Australia coach] Bob Dwyer. I feel for the other guys but I know if we call on them they will be ready."

Former skipper Dylan Hartley is currently not available for selection because of a lingering knee issue, with Jones unable to confirm whether the Northampton man would come into the picture if he proved his fitness.

"We don't deal with hypotheticals, but if that situation does occur we will have a good think about it," Jones said.

Although the make-up of the final 31 has now become much clearer, Jones says the door remains open for World Cup 'bolters' such as Northampton flanker Lewis Ludlam and Bath's former Sevens winger Ruaridh McConnochie, who are both uncapped and have come from nowhere to make the training squad.

"You are always looking for a couple of 'X-factor' players that come through later and are in form and excite the squad and the fans," Jones said.

"Lewis and Ruaridh have done that with outstanding performances for their club. They both have great desire and good character."

Jones will name his final World Cup squad on 12 August, shortly after the first of England's four warm-up matches.

"It's a moveable feast, but we have a pretty good idea of at least probably 28 of the players [for the final squad]," he said.

"Out of the squad of 38 we will get 31 players with the necessary experience, skill and desire to win the Word Cup for England."