Everton midfielder Darron Gibson will be out for four to five weeks with a thigh strain.
The 24-year-old has figured in all three of the Toffees' Barclays Premier League matches so far this season but was forced off 20 minutes into the first half of the most recent contest, a 2-0 defeat at West Brom on September 1.
Toffees boss David Moyes, however, remains hopeful the former Manchester United midfielder could make a quicker-than-expected return.
The Scot explained: "Darron's got a thigh strain and will probably be out for four to five weeks now.
"He's had two weeks now so hopefully we are a couple of weeks down the line already because of the international break - so he may have only a couple of weeks to miss."
Gibson recently told Republic of Ireland manager Giovanni Trapattoni he was still suffering from the disappointment of playing a limited role at the Euro 2012 finals and did not want to be considered for selection in their World Cup qualifying campaign.