One of the benefits (for the teams, anyway) of having a draft class as deep as the 2017 running back class is that potential gems have a way of slipping through the cracks.
While the New York Giants certainly seem to like 2016 draftee Paul Perkins, by parting ways with veteran running back Rashad Jennings, they likely have opened a vacancy that could be filled by a rookie running back. Mack is versatile, athletic, and highly productive in college. Mack also had a very good workout at the NFL Scouting Combine, which saw him stand out in the on-field drills.