Wales manager Chris Coleman says he does not know when midfielder Aaron Ramsey will return from injury.
Ramsey has not played since injuring his hamstring while playing for Arsenal in their opening-day Premier League defeat by Liverpool on 14 August.
The initial estimate was three weeks, but the 25-year-old will miss Wales' 2018 World Cup qualifiers against Austria and Georgia in October.
"The disappointment is we expected him to be here," said Coleman.
"I had an indication that he would only be out for three weeks when he initially did it. That was six weeks ago - so I don't know now.
"I have had more information from Sean [Connelly], our head physio who is liaising with Arsenal, that he has broken down in training. We have not yet been given a date on when he will definitely be back."
Ramsey missed Wales' 4-0 win over Moldova in their opening World Cup qualifier in September.
Arsenal manager Arsene Wenger said the former Cardiff City midfielder would be "back after the [September] international break" but Coleman says he may now even be a doubt for Wales' match against Serbia in November.
"I was sure in the last camp I would have him for this camp," said Coleman.
"It's a huge disappointment not to have Rambo. That's 30% of the campaign without one of our best players. If you take him out of any team, it will have an impact."
Before Wales' opening victory against Moldova, Coleman had said Ramsey's injury for Arsenal could "possibly" have been prevented.
His comments revived a disagreement he had with Wenger over Ramsey last year, where the roles were effectively reversed.
Asked about Ramsey's current injury, Coleman again feels his lengthy absence might have been avoided.
"It is frustrating. It is preventable. I don't know the exact history of what he has been doing the last six weeks," he added.
"Our physio will get more information, so it is hard to comment on whether he was pushed too hard or not enough.
"Could that have been prevented in the way he was looked after when he got back from the tournament? I don't know. But you can't help but think, if only."