Bristol City face being without captain Louis Carey for an extended period after scans revealed the defender has a torn calf muscle.
Carey took a kick on the calf during the defeat at Leeds on November 13 and was expected to return to action against Derby this weekend but after suffering further discomfort during training a scan has revealed a much more serious injury than first thought.
"Louis has no chance for the Derby game and I'm not even considering him," Millen told the Bristol Evening Post.
"He did a training session the Monday before last and complained of discomfort in his calf after he had finished. We sent him to hospital for a scan as a precaution and were surprised when it showed up a tear in the muscle.
"Having thought he would be out for two to three weeks, we've now had to revise the date for his comeback."
Copyright (c) PA Sport 2009, All Rights Reserved.