Gilbert dislocated his shoulder on Tuesday in training and has had to go to London to see a specialist and he may require surgery.
After that he will return to Cardiff and continue his rehabilitation at Ninian Park.
Gilbert would have retuned to the City side this weekend after serving a suspension but the injury, upon whcih the club will make no guess of the time expected to be out, means that City are looking to extend James Chambers' loan spell.
He came to cover Kevin McNaughton's injury and found himself cover Gilbert's suspension. Now he's set for a longer run in the side.