Jamie McCombe will undergo surgery early next week after suffering a fractured cheekbone against Derby.
The Bristol City defender picked up the injury just 13 minutes into the Robins' 1-1 draw with the Rams.
He was caught in the face by the knee of Claude Davis and is now facing a frustrating spell on the sidelines.
"It's a blow for us and Jamie and it's likely he will be out for around six weeks," City boss Gary Johnson told the club's official website.
Johnson is also still waiting on Liam Fontaine to shake off an ankle problem and admits that he may be forced to enter the transfer market before the window slams shut at the end of the month.
"Liam's injury is not serious, but I still think we will have to bring in a new centre-back and I'll be going straight off to look through my book of contacts," he said.