Midfielder Aaron Ramsey looks likely to miss Wales' World Cup qualifying matches next month.
Ramsey, 25, injured a hamstring in Arsenal's opening Premier League game of the season against Liverpool.
Gunners boss Arsene Wenger said: "I don't think Ramsey will be available before the international break."
Wales opened their campaign with a 4-0 win over Moldova and play Austria on 6 October followed by Georgia in Cardiff three days later.
"There is concern because he has been out for so long," Wales assistant boss Osian Roberts told BBC Wales Sport before Wenger's latest comments.
"It's extremely disappointing after the magnificent tournament Aaron had at the Euros that he picked up an injury in the opening game of the season.
"It's a huge disappointment for him and for all of us. But let's just hope the situation improves for him."
Ramsey was Wales' outstanding player at Euro 2016, but was suspended for the 2-0 semi-final defeat by Portugal.