Wales second row Cory Hill could “possibly” be out of the World Cup without playing a game, says coach Warren Gatland.
Hill is recovering from a stress fracture in a leg, with Adam Beard recovering from appendicitis surgery.
Asked if Hill was out of the tournament, Gatland said: “Possibly.”
He added: “In terms of fitness he will go back to the UK if he is not right. We will assess him tomorrow and just see what progress he has made and how his injury is.
“If it is not good news then he will go back. If they think they can get him to recover then he will stay out. We are just going to assess it overnight.”
Wales face Australia in Tokyo on Sunday, 29 September, with Beard already ruled unlikely to be fit.
If Hill has to return home, his place is likely to be taken by Ospreys second row Bradley Davies.
If neither player is fit it could mean captain Jones and Scarlets’ Australian-born Ball will have to pack down for the second time in seven days in a match which could decide the eventual winners of Pool D.
Centre Hadleigh Parkes suffered what Gatland described as a “bit of a bone fracture” in his hand in the six-try win against Georgia, but said the New Zealander will be “OK to pad that up and it should not be an issue for him for selection next week”.