Wales coach Chris Coleman is waiting to learn whether Joe Allen will be fit to face Serbia after the midfielder was a late withdrawal against Belgium.
Allen was scheduled to start Wales' opening 2014 World Cup qualifier against Belgium on Friday night, but was forced to pull out due to illness.
The Liverpool new boy was one of several influential players to miss the 2-0 defeat, with the likes of Craig Bellamy and Neil Taylor also absent.
Serbia are Wales' next opponents on Tuesday night and Coleman was disappointed to be without Allen against the favourites to win Group A.
"It was a bitter blow to find out we wouldn't have him," said Coleman.
"He had a temperature and sickness and we will see in the next 24 to 48 hours how he comes through it.
"With our strongest XI it would have been a tough game - and when you take half a dozen players out, lose Joe Allen eight hours before the game and you go down to 10 men then you've got a mountain to climb."
Wales had James Collins sent off after 26 minutes before goals from Vincent Kompany and Jan Vertonghen earned Belgium the points at the Cardiff City Stadium.