BATH centre Jonathan Joseph is a doubt for England's key World Cup clash with Wales on Saturday due to a chest injury.
England backs coach Andy Farrell revealed that Joseph's fitness would be determined one way or another by Wednesday.
"JJ has a bit of a knock, nothing too serious and we're working hard to get him fit," Farrell said at an England press conference at the team base in Surrey ahead of Saturday's Pool A encounter at Twickenham.
"We'll give JJ every chance to prove his fitness. We'll know if he's fit tomorrow. If he's not, then it's only a week long injury."
If Joseph is ruled out by injury it would be a big blow for England head coach Stuart Lancaster as the Bath centre is a potential matchwinner.
Lancaster has several options to replace Joseph, with Henry Slade and Sam Burgess the other specialist centres in his squad while fly-half Owen Farrell has got experience of playing at centre.
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