Ollie Lawrence and Jack Walker face a race against time to be ready for England’s World Cup warm-up matches after suffering minor injuries in training.
Bath powerhouse Lawrence has picked up a knee issue and Harlequins hooker Walker a calf complaint.
Lawrence and Walker have linked up with the England training camp that has moved to Brighton this week, for rehabilitation.
Head coach Steve Borthwick has extended his training ranks to 38, taking advantage of the availability of players from Northampton and Leicester after the end of the Premiership semi-finalists‘ rest period.
Leicester-bound wing Ollie Hassell-Collins and scrum-half pair Harry Randall and Ben Spencer have been omitted from the training squad after being included in last week’s gathering at Pennyhill Park.
The availability of Saints and Tigers players means scrum-halves Alex Mitchell, Ben Youngs and Jack van Poortvliet have all joined the squad, with Harlequins’ Danny Care also retained.
Bath centre Lawrence and Quins hooker Walker both boosted their England status across the Six Nations under Borthwick, with the pair developing into important Test options.
England are understood to hope to see both men back in training by the end of July, which would tee up a chance to feature in the four World Cup warm-up matches in August.
“After an excellent first week’s training we are very much looking forward to being in Brighton,” said Borthwick.
“We’re pleased to welcome players from Northampton Saints and Leicester Tigers who can now start to integrate themselves into the group, and we look forward to players from Sale Sharks and Saracens joining us in a fortnight.
“The first phase of our preparation continues to focus on ensuring the players are physically equipped for what we need to do in a World Cup campaign. That means the training will be tough and purposeful. The players are rising to the challenge.
“We’ll work hard again this week, and we’ll enjoy some time together off the field too, which is also an important part of our preparation.”
Leicester’s Dan Cole and Joe Heyes swell the ranks at prop, with Courtney Lawes, Lewis Ludlam and David Ribbans adding back-five Saints beef.
Tigers lock George Martin has a chance to impress after a fine season at Welford Road, while Saints backline trio Fraser Dingwall, Tommy Freeman and Fin Smith all join the squad.
Leicester centre Guy Porter gets the nod to bolster the midfield options, with full-back Freddie Steward and wing Anthony Watson nailed-on additions.
Billy Vunipola, Ollie Chessum and Luke Cowan-Dickie are all staying with the England camp to continue injury rehab.
England’s 38-player training squad
Forwards: J Blamire (Newcastle), D Cole (Leicester), A Dombrandt (Harlequins), T Dunn, C Ewels (both Bath), E Genge (Bristol), J Heyes (Leicester), T Hill (Bath), C Lawes, L Ludlam (both Northampton), J Marler (Harlequins), G Martin (Leicester), Z Mercer (Montpellier), B Obano (Bath), T Pearson (London Irish), V Rapava-Ruskin (Gloucester), D Ribbans (Northampton), K Sinckler (Bristol), W Stuart, S Underhill (both Bath).
