England second row George Kruis is a major doubt for his side's Six Nations opener against France on Saturday.
Kruis has only recently recovered from a fractured cheekbone and last week received the all-clear to play in the opening match of England's title defence at Twickenham.
However, the lock was forced to miss training on Tuesday having picked up knee ligament damage, and he will now see a specialist on Thursday to determine whether he will be able to feature in the tournament.
"We'll have to wait and see what the specialist's prognosis is, but we're not ruling him out of the RBS Six Nations at this stage," head coach Eddie Jones told reporters.
Assistant coach Paul Gustard added: "George is with our medical group and they're assessing how he is. We've had our meetings as coaches this morning and medical have been looking after the players. I don't know how the assessment has gone.
"We pride ourselves as a nation about the quality we have around the country. As a coaching group from day one we were very excited about the talent we've got in English rugby at the moment.
"We're proving we can cope with people not being in the team and while there are people missing in this Six Nations there are also people returning and that's also exciting. The likes of Maro Itoje and James Haskell coming back into the group is encouraging."
England will be looking for a record-breaking 15th consecutive win when they welcome France to Twickenham.
