There was a lot of optimism surrounding Williams early in camp, but that was long forgotten after he dropped back-to-back passes against Cincinnati in the first preseason game. It's tough to give up on a third-round pick, but Williams was given more than a fair chance in Detroit.
Brown likely won his roster spot during the Patriots game. Overall, Brown had a pretty impressive preseason, but his performance against the Patriots was special. It is still unclear how many backs the Lions will keep, but it appears Jerome Harrison's spot may be in danger.
UPDATE: Lions have announced that they will not release full 53-man roster until 8 PM. Looks like we'll be waiting a little longer than expected (cuts must be made by 6 PM).