Northampton Saints flyhalf Stephen Myler and Wasps centre Elliot Daly, plus Saracens forward Maro Itoje and Leicester Tigers's Ed Slater will return to their clubs and be on standby.
Number eight Nick Easter has been left at home for treatment to a back injury but the 36-year-old will return to the squad in August once England have returned from Denver.
"Elliot and Maro have fitted in and trained well and it's been great for them to be in this environment," Lancaster told the RFU website (www.englandrugby.com).
"Steve and Ed, likewise, have contributed greatly. I have spoken to all the players to explain that things can change very quickly and they can come back in at any point.
"Denver is the next stage in our training, a chance to develop further in a different environment."
England will play three warm-up games, two against France and one against Ireland, before the World Cup opener against Fiji on Sept. 18.
England training squad for Denver: Chris Ashton (Saracens), Dave Attwood (Bath Rugby), Brad Barritt (Saracens), Kieran Brookes (Northampton Saints), Mike Brown (Harlequins), Luther Burrell (Northampton Saints), Sam Burgess (Bath Rugby), Danny Care (Harlequins), Danny Cipriani (Sale Sharks), Calum Clark (Northampton Saints), Dan Cole (Leicester Tigers), Alex Corbisiero (Northampton Saints), Luke Cowan-Dickie (Exeter Chiefs), Lee Dickson (Northampton Saints), Kyle Eastmond (Bath Rugby), Owen Farrell (Saracens), George Ford (Bath Rugby), Alex Goode (Saracens), Jamie George (Saracens), James Haskell (Wasps), Jonathan Joseph (Bath Rugby), Courtney Lawes (Northampton Saints), Joe Launchbury (Wasps), George Kruis (Saracens), Matt Kvesic (Gloucester Rugby), Joe Marler (Harlequins), Jonny May (Gloucester Rugby), Ben Morgan (Gloucester Rugby), Matt Mullan (Wasps), Jack Nowell (Exeter Chiefs), Geoff Parling (Exeter Chiefs), Chris Robshaw (Harlequins), Semesa Rokoduguni (Bath Rugby), Henry Slade (Exeter Chiefs), Billy Twelvetrees (Gloucester Rugby), Mako Vunipola (Saracens), Billy Vunipola (Saracens), Anthony Watson (Bath Rugby), Rob Webber (Bath Rugby), Richard Wigglesworth (Saracens), David Wilson (Bath Rugby), Tom Wood (Northampton Saints), Marland Yarde (Harlequins), Ben Youngs (Leicester Tigers), Tom Youngs (Leicester Tigers).
(Reporting By Michael Hann; editing by Amlan Chakraborty)
Share
