On-loan striker Sam Vokes is set to have a scan to determine the extent of the hamstring injury suffered on his Bristol City debut.
Vokes, on loan from Wolves, lasted just 13 minutes after coming off the bench as a second-half substitute in City's 3-0 home defeat to Millwall on Saturday.
The Wales international has been forced to withdraw from John Toshack's squad to face Luxembourg on Wednesday as a result.
"Sam needs to go and have a scan. He is still very sore and will be out for a while but we don't know how long yet," manager Steve Coppell told the club's official website.
"If he is going to be missing for some time then it is likely he will go back to Wolves to receive treatment. If it is not so bad then he will probably remain here."