Gallagher has been on loan at Preston this season and manager Alan Irvine is keen to have him back, but Williams is not sure Mark Hughes will let him go.
"It's a decision for the manager," said Williams. "Mark has always admired Paul and if he feels he has a role to play then he'll stay with us and that could happen.
"But, if not, Paul could go back out on loan. We'll just have to wait and see."