Bath's Beno Obano could be out for up to 12 months after suffering "multiple ligament and hamstring tendon damage" while training with the England squad.
Prop Obano, 23, who was first called into Eddie Jones' squad in December, was among 16 uncapped players involved in last week's camp in Brighton.
Obano signed a new deal with Bath earlier in May and now faces surgery.
"We are all feeling Beno's disappointment," said Bath director of rugby Todd Blackadder.
"It's upsetting to see that he will miss this chance to show his class at an international level. It's been a breakthrough season for him.
"We know Beno will do everything he can to get back on the pitch and in the blue, black and white as soon as he can.
"Whilst this type of injury is complex and can lead to a 12 month lay-off, we are investing in our medical team over the off-season and we are focused on getting Beno back as soon as possible."