England flanker Joe Worsley looks likely to miss the Calcutta Cup clash against Scotland at Murrayfield on Saturday.
The Wasps forward has a hamstring injury, and is rated "very doubtful" for the game by England head coach Sir Clive Woodward.
Sale Sharks flanker Alex Sanderson has joined the England squad at its Surrey training base.
Worsley was injured during England's 50-9 RBS 6 Nations Championship victory over Italy in Rome, but Woodward has reported that there were no other major injury concerns, although scrum-half Andy Gomarsall is nursing a slight knock.
As a result, Bath's Martyn Wood has also reported for training, but Woodward is confident that Gomarsall will make it.
England captain Lawrence Dallaglio and centre Jason Robinson, who also suffered knocks in Rome, are fit and available for selection.
"Joe Worsley is very doubtful for the game, and he will be going for a scan today (Tuesday)," said Woodward.
"Alex Sanderson is coming down to join us, and I will be surprised if Worsley is available for Scotland."
If, as seems likely, Worsley is ruled out, then Woodward could either draft Sanderson straight into his team, or reshuffle the back row by switching Dallaglio from number eight
to blindside flanker and calling up Chris Jones off the bench.
Jones made an impressive England debut in Rome, going on and scoring his team's seventh and final try.
Wood, meanwhile, is used to providing injury cover for the England squad.
He was flown to Australia during the World Cup campaign last October as a precaution while Matt Dawson and Kyran Bracken recovered from injuries. Wood spent almost three days Down Under, but then returned home again without ever officially joining the squad.
Andy Farrell admits the process of selecting England's 50-man training squad ahead of the World Cup was rigorous - but the backs and defence coach also revealed how tough it was to leave some stars out.