Sale Sharks fly-half Danny Cipriani, Harlequins No.8 Nick Easter and uncapped Leicester Tigers lock Graham Kitchener are the notable inclusions in England's initial 34-man Six Nations squad for the championship opener against Wales at the Millennium Stadium.
Kitchener is promoted from the Saxons squad to replace Courtney Lawes, who underwent ankle surgery earlier this week.
Cipriani, 27, is one of four half-backs included in the training party while Easter is included nearly four years on from his last international cap in 2011 and comes in for Ben Morgan, who has a broken leg.
Selection for Cipriani comes after the player threatened to quit English rugby entirely and move to Toulon, where he would become unavailable.
England coach Stuart Lancaster is without Morgan, Joe Launchbury and Ben Foden for the duration of the tournament but could yet call upon the currently sidelined Manu Tuilagi and Lawes later in the competition despite their initial omission.
Five members of the victorious British and Irish Lions tour to Australia in the summer of 2013 are recalled after missing the autumn internationals due to injury with Alex Corbisiero, Dan Cole, Geoff Parling, Tom Youngs and Mako Vunipola all included.
Chris Robshaw is confirmed as captain for the Six Nations to continue Lancaster's policy of selecting his skipper based on form and fitness alone.
"We have plenty of players to consider and with some players still being assessed from last weekend after suffering knocks we have kept our options open," Lancaster said.
"It's a big European weekend ahead and there may be further changes once we assess the fitness of the players after round six and we will provide an update on Monday.
"We will use the four-day training camp and the Saxons game to narrow down selection as we lead into the opening game against Wales.
"The match against the Wolfhounds in Cork gives us a great opportunity to take a look at a group of players who are right on the edge of the senior squad and we also have the likes of David Strettle and Freddie Burns, who are very much in our thinking as options going forward.
"We will be without Joe Launchbury and Ben (Morgan) and it was a real shame to see Ben Foden pick up his injury up last weekend. We will continue to work with Northampton Saints and Leicester Tigers with Courtney and Manu and see where they are as the Six Nations progresses."
England begin their Six Nations campaign against Wales on 6 February, before taking on Italy, Ireland, Scotland and France in a key precursor to the World Cup on home turf starting in September.
Meanwhile, Bath centre Sam Burgess is the headline call-up to the England Saxons squad for the match against Ireland Wolfhounds in his first international recognition since switching codes from Rugby League.
Maro Itoje, captain of the victorious England Under-20 side at the Junior World Championships is also selected while Kieran Brookes, the returning Tom Croft, Chris Ashton, Marland Yarde and Christian Wade will be among those aiming to impress.
England senior squad
Dave Attwood, Calum Clark, Dan Cole, Alex Corbisiero, Nick Easter, Dylan Hartley, James Haskell, Graham Kitchener, George Kruis, Joe Marler, Geoff Parling, Chris Robshaw, Billy Vunipola, Mako Vunipola, David Wilson, Tom Wood, Tom Youngs
Brad Barritt, Mike Brown, Luther Burrell, Danny Care, Danny Cipriani, Kyle Eastmond, Owen Farrell, George Ford, Alex Goode, Jonathan Joseph, Jonny May, Stephen Myler, Jack Nowell, Billy Twelvetrees, Anthony Watson, Richard Wigglesworth, Ben Youngs
England Saxons squad
Kieran Brookes, Tom Croft, Christian Day, Luke Cowan-Dickie, Dave Ewers, Matt Garvey, Ross Harrison, Maro Itoje, Matt Kvesic, Matt Mullan, Henry Thomas, Thomas Waldrom, Alex Waller, Rob Webber
Chris Ashton, Sam Burgess, Elliot Daly, llie Devoto, Lee Dickson, Chris Pennell, Joe Simpson, Henry Slade, Marland Yarde, Christian Wade