Exeter wing Jack Nowell is highly unlikely to feature in England's first World Cup warm-up match against Wales on 11 August.
Nowell returned home from England's training camp in Italy for a routine medical assessment as he continues to recover from ankle surgery.
He will continue rehabilitation at his club, with the first of England's two camps in Treviso ending on Friday.
The 26-year-old has won 33 caps since making his debut in 2014.
The World Cup takes place in Japan from 20 September to 2 November, with England coach Eddie Jones set to finalise his World Cup party the day after the game against Wales at Twickenham.
England will also play Wales in Cardiff and Ireland at Twickenham, before their final pre-World Cup game against Italy in Newcastle on 6 September.