Martin Kelly was forced to sit out England training earlier today with a virus.
The Liverpool defender, who was called into the squad recently as a replacement for Gary Cahill, has now been rated a doubt to feature in Monday's opening match against France.
The 22-year-old was the only member of the 23-man squad to miss the session, with John Terry and Ashley Cole appearing to have recovered from injury and illness respectively.
Kelly made his one and only appearance for the Three Lions as a substitute during a recent friendly against Norway.