London - Joint England captain Dylan Hartley and skipper at the tournament four years ago Chris Robshaw look set to miss this year's Rugby World Cup after being omitted from a training squad named by Eddie Jones on Thursday.
Hartley - who under Jones lead England to two Six Nations titles including the 2016 Grand Slam - has struggled with concussion and now a knee injury, which it is believed will leave the combative hooker short of match fitness come the start of the tournament in Japan in September.
Robshaw shouldered a lot of the blame for the humiliating first round exit from the 2015 World Cup on home soil, but had reclaimed a place in the team before having knee surgery in October.
Jones has also omitted another experienced performer in scrumhalf Danny Care - the second most capped England player in his position with 84 Tests to his name.
Care played in last autumn's Tests against South Africa and world champions New Zealand, as well as scoring a try against Japan, but was dropped for the match with Australia and did not appear in this year's Six Nations.
By contrast, veteran fullback Mike Brown makes the group though he has lost his starting place to Elliott Daly.
The uncapped Alex Dombrandt is picked after catching Jones' eye in the non-Test status clash with the Barbarians earlier this month.
Ben Youngs and Dan Robson are the scrumhalves called up, whilst it is expected Gloucester's Willi Heinz and Saracens' Ben Spencer will also figure in a future training camp.
That duo like other players who featured in the Premiership semi-finals and final are automatically given five weeks off and are not included.
Players from beaten semi-finalists Northampton and Gloucester can be called up next week with those from champions Saracens and runners-up Exeter players available the following week.
Jones names his final training party on July 4.
England's preliminary Rugby World Cup squad which takes place in Japan between September 20-November 2:
Dan Cole (Leicester Tigers), Tom Curry (Sale Sharks), Alex Dombrandt (Harlequins), Tom Dunn (Bath), Charlie Ewels (Bath), Ellis Genge (Leicester Tigers), Joe Launchbury (Wasps), Lewis Ludlam (Northampton Saints), Val Rapava Ruskin (Gloucester), Nick Schonert (Worcester Warriors), Brad Shields (Wasps), Kyle Sinckler (Harlequins), Jack Singleton (Worcester Warriors), Sam Underhill (Bath), Mark Wilson (Newcastle Falcons)
Chris Ashton (Sale Sharks), Mike Brown (Harlequins), Joe Cokanasiga (Bath), Elliot Daly (Wasps), George Ford (Leicester Tigers), Jonathan Joseph (Bath), Jonny May (Leicester Tigers), Ruaridh McConnochie (Bath), Dan Robson (Wasps), Marcus Smith (Harlequins), Ben Te’o (Worcester Warriors), Manu Tuilagi (Leicester Tigers), Anthony Watson (Bath) Ben Youngs (Leicester Tigers).
In for medical treatment George Kruis (Saracens) Mako Vunipola (Saracens)