Nottingham Forest expect Ishmael Miller to be sidelined for up to four weeks after being forced to undergo a hernia operation.
The striker was ruled out of Tuesday's 1-0 victory over Reading when it became apparent that he would require surgery.
Miller has been carrying the complaint for some weeks and has been prepared to play through the pain.
It was hoped that he would make it to the international break before going under the knife, but the procedure has been brought forward.
Miller was in such discomfort following a 1-0 reversal against Hull City on Saturday that the decision was taken to send him for surgery right away.
Forest expect the 24-year-old to be out of action for at least three weeks, but hope he will be back for the busy Christmas period.