The goalkeeper was brought in on a month's loan while Matt Duke recovered from a back injury. He made a handful of appearances for the reserves - helping them maintain their unbeaten run this season - and warmed the first team bench while Boaz Myhill retained the number 1 shirt.
Duke should now be fit to start playing again after suffering his injury 7 weeks ago. He was among the un-used substitutes for the FA Cup game against Morecambe earlier this month, before Brock was back on the bench for Saturday's defeat at Swindon.
He may have to wait for the next reserve fixture though as Wednesday's match with Barnsley has been postponed.