Jason Demetriou picked up his fifth booking of the season against Brighton in midweek and is banned for Saturday's clash with Colchester along with fellow midfielder JJ Melligan, while injury doubts linger over Adam Chambers, Sean Thornton and Stephen Purches.
"The disappointing thing was Jason Demetriou's booking," said Williams.
"That takes him to five and that means he is suspended on Saturday. I thought he had his best game of the season.
"With JJ Melligan also suspended and injuries that leaves us a bit thin on the ground."