Joe Launchbury continues to be a major doubt for Saturday's first Test against South Africa but England will give him every chance to prove his fitness.
The in-form Wasps captain was once again unable to train with Eddie Jones' squad at Kings Park on Wednesday due to the calf injury sustained in practice last week.
Launchbury is set to form a second-row partnership alongside Maro Itoje if fit, with Nick Isiekwe and Jonny Hill the alternatives if he fails to recover in time.
England name their team for the series opener against the Springboks at Ellis Park on Thursday and are hopeful that their veteran lock will be involved.
"We're giving Joe the best possible chance to play this weekend," defence coach Paul Gustard said.
"He's on a modified programme. We'll have to assess how he came though today (Wednesday). We'll assess it later on when we have our selection meeting."
The uncertainty over Launchbury is the only injury concern as selection is finalised for England's attempt at halting their four-match losing run