Cook (6-4, 215), a third-year player out of Michigan State, was originally a fourth-round draft pick of Oakland in 2016. He played in one regular-season game for the Raiders, and passed 14 of 21 for 150 yards, with one TD and one INT. He was released by Oakland at final cuts this season, before later spending time on Carolina’s practice squad.
Vollert (6-5, 245), a rookie out of Weber State, originally signed with Arizona as a college free agent in May. He played in all four preseason games for the Cardinals, and caught eight passes for 55 yards. He was waived at final cuts, then signed to the Cardinals’ practice squad, where he spent the first eight games of the season before being released on Oct. 30.
Hackenberg, a third-year player out of Penn State, had signed to the Bengals practice squad on Sept. 3.