Northern Ireland defender Gareth McAuley could miss the Euro 2012 qualifiers against Serbia and Estonia early next month because of illness.
The West Brom player was forced off at half-time in Wednesday's win over the Faroe Islands after feeling unwell.
"Gareth has been ill over the course of pre-season with West Brom," said NI manager Nigel Worthington.
"We thought it had cleared up but he started to feel unwell in the first half and was very weak at half-time."
He added: "Hopefully, it is something his club can get to the bottom of and get rectified.
"We hope when he comes back (for the qualifiers) in three weeks he is back to his normal strength."
Northern Ireland, who sit third in Group C, are home to Serbia on 2 September before travelling to take on Estonia four days later.
McAuley moved from Ipswich Town to West Brom on a free transfer in May.
The 31-year-old is unlikely to be fit for the opening Carling Premiership game against champions Manchester United at the Hawthorns on Sunday.