Former Plymouth defender Gilbert found out earlier today that he will be out for around nine months after suffering extensive knee ligament damage.
He had been playing through the pain barrier in recent games but was taken off early doors at Wolverhampton to be replaced by Hills.
It is a massive blow to Wednesday who have had Steve MacLean and David Lucas out this season with similar problems.
Steve Adams and JP McGovern are also ready to take their places on the bench for the Clarets clash