Derby defender Shaun Barker faces a spell on the sidelines in the latest injury blow to rock the club.
The summer signing from Blackpool has suffered a recurrence of the thigh strain that kept him sidelined at the start of the season.
County have not put a timescale on how long the centre-half is expected to be out but it could be up to a month.
"It's a big blow because Shaun was starting to settle in and had a very good game against Sheffield Wednesday in our last game," Rams boss Nigel Clough told the club's official website.
"We are not prepared to put a specific time frame on the lay-off except to say it looks like being a number of weeks."
The Rams will be without eight players through injury when they resume their Championship campaign at Midlands rivals Leicester at the weekend.
Clough hopes Dean Leacock can recover from a hamstring problem to partner Jay McEveley at centre-half.