England coach Steve Borthwick says the "positional flexibility" of players was an "important aspect" of his squad selection for the Rugby World Cup.

"There are good players unfortunately that you can't select," said Borthwick.

"I'd love there to be more than 33 I can pick, but I can't. Being limited to that, players will miss out."

Slade, who was picked for the previous two World Cups, has appeared in 30 of England's past 37 Tests and was the highest-profile omission from the squad for the upcoming tournament in France.

Asked about his absence, Borthwick said: "There are good players competing for each of these positions. I decided we'll have three players in key positions - front row, scrum-half, fly-half - for the obvious reasons.

"What that means is in other areas of the team, you need to have positional flexibility and you need to make some compromises.

"As you look at the squad, there are a number of players who can play 12 or 13. Joe [Marchant] gives you that wing cover, Elliot Daly, Ollie Lawrence and Manu Tuilagi can play 13, you've got the ability of Owen [Farrell] to play at 10 or 12.

"We've got flexibility throughout the centres, which has been an important aspect."

Another talking point from Borthwick's final selection is the inclusion of only one specialist number eight, Billy Vunipola, who has not played since April because of a knee injury.

Borthwick said the Saracens player is "as fit as I've ever seen him" and believes he has plenty of additional options in that area.

He added: "There's a lot of competition in that back row, there's also flexibility in that back row around positions. You've got Lewis Ludlam's ability to play in all three, Ben Earl's ability to play seven and eight, Tom Curry at seven and eight and at the last World Cup he played six.

"There's a lot of flexibility there, for me it's about making decisions about the right combinations and ultimately that's what it's come down to."

'It's a fantastic tournament - you don't want to waste one'

There is a mixture of youth and experience within the England squad, with 16 players surviving from the group that was beaten in the 2019 final by South Africa in Japan.

Versatile Racing 92 back Henry Arundell, 20, is the youngest man selected while three players - Ben Youngs, Courtney Lawes and Dan Cole - will be appearing at their fourth World Cup.

Captain Owen Farrell spoke at a media conference on Monday alongside centre Lawrence, back row Earl and scrum-half Jack van Poortvliet, three of 16 players who will be experiencing a World Cup for the first time.

Farrell said: "I can only sit here and tell them how special it is, what a tournament we're about to play in, what an opportunity we've got to get the best of ourselves and to enjoy taking the best of ourselves to the rest of the world.

"It's a fantastic tournament, one that comes around every four years. You don't want to waste one. This is as good as it gets. We're all looking forward to it."

Farrell added that he planned to speak to Slade, who he said he had been sharing a room with during England's training camp for the past four weeks.

"The boys that have just missed out are a big part of this preparation," added the Saracens fly-half. "When it comes to any squad, there's a lot of competition and especially with England where there are a lot of good players.

"There were always going to be good players that missed out. That's always the case with squads here."

Sleepless nights and tearful parents - the emotions of a World Cup call-up

Earl's place in the 33-man party was confirmed in a conversation with Borthwick on Sunday morning, the day after England's disappointing warm-up loss to Wales in Cardiff.

The Saracens man said: "It was very early, about nine o'clock in the morning so I'd just got up as I'd had a bit of a sleepless night.

"The conversation I had with him was really encouraging in terms of what he wanted out of me.

"The thing Steve's done since he's come in is he's really encouraged us to be the players we are and not fit into another mould or try to be something different. He wants to see our strengths and how we can put our best foot forward."

While Earl's inclusion was slightly in the balance, Van Poortvliet was widely expected to be named as one of three scrum-halves in Borthwick's squad.

Van Poortvliet, who will compete with Leicester team-mate Ben Youngs and Harlequins' Danny Care to start at nine, broke the news of his call-up to his family in a phone call while they were on a car journey.

"My sister had just moved her stuff into her new university house," he said. "My mum cried a lot which was pretty hard to deal with, but it was really nice and really special."

England begin their World Cup campaign against Argentina in Marseille on 9 September, with Japan, Chile and Samoa their other opponents in Pool D.

Before their World Cup opener, Borthwick's team will play warm-up fixtures against Wales (12 August), Ireland (19 August) and Fiji (26 August).