Manu Tuilagi and Luke Cowan-Dickie are absent from England's training squad for their three-day camp in Bristol this week, while Jonny Hill is again missing.
Tuilagi is recovering from a hamstring strain and Cowan-Dickie is waiting to discover how serious the knee injury incurred in Saturday's 23-19 Guinness Six Nations win over Wales is.
Tom Curry is overcoming the concussion sustained at Twickenham in Round 3 so Gloucester's Lewis Ludlow has been called up as back-row cover.
Alongside Tuilagi, Hill has been unable to take part in this Six Nations because of a high ankle stress fracture, but the Exeter lock is to continue his rehab with England.
Uncapped London Irish prop Will Goodrick-Clarke has been included, but Elliot Daly and George Ford are omitted from the 25-man squad who will begin preparations for the clash with Ireland on March 12.
Eddie Jones has opted to keep Marcus Smith as the only specialist fly-half in camp, so Ford will be present to direct Leicester in Saturday's match against Saracens.
Daly, meanwhile, has failed to leave his mark at outside-centre and so Joe Marchant will be given another chance after being parachuted on to the bench against Wales once Tuilagi had been ruled out.
England's 25-man training squad for three-day Bristol camp
Forwards (15): Alfie Barbeary (Wasps, uncapped), Jamie Blamire (Newcastle Falcons, 5 caps), Alex Dombrandt (Harlequins, 7 caps), Charlie Ewels (Bath Rugby, 29 caps), Ellis Genge (Leicester Tigers, 34 caps), Jamie George (Saracens, 64 caps), Will Goodrick-Clarke (London Irish, uncapped), Maro Itoje (Saracens, 54 caps), Nick Isiekwe (Saracens, 6 caps), Joe Launchbury (Wasps, 69 caps), Courtney Lawes (Northampton Saints, 91 caps), Lewis Ludlow (Gloucester Rugby, 2 caps), Sam Simmonds (Exeter Chiefs, 12 caps), Kyle Sinckler (Bristol Bears, 50 caps), Will Stuart (Bath Rugby, 18 caps).
Backs (10): George Furbank (Northampton Saints, 5 caps), Ollie Hassell-Collins (London Irish, uncapped), Max Malins (Saracens, 13 caps), Joe Marchant (Harlequins, 10 caps), Jack Nowell (Exeter Chiefs, 37 caps), Harry Randall (Bristol Bears, 4 caps), Henry Slade (Exeter Chiefs, 46 caps), Marcus Smith (Harlequins, 8 caps), Freddie Steward (Leicester Tigers, 8 caps), Ben Youngs (Leicester Tigers, 115 caps).