You can view Theo Riddick's complete scouting report here (via B/R featured columnist Dan Tylicki).
Riddick is at his best when making defenders miss, not when running through them—although he did both at Notre Dame. He also isn't afraid to get involved in pass protection, and caught a whopping 120 passes in his four-year career, and 114 in the past three years alone. Per Tylicki:
Riddick's biggest strength is his versatility. He was used as a slot receiver his sophomore and junior years, and his career receiving yards are better than his rushing numbers (1,263 vs. 1,169). As a wideout, he has developed great hands and can be used in both roles.
He is not a running back that goes down on the first hit, as he is able to stay upright, and his toughness should translate well to the NFL. His quick feet provide great acceleration and he shows the ability to run past the first batch of defenders.
Beyond that, Riddick has the ability to stop on a dime and change course when needed. He may not be an open-field runner, but if a safety is closing in on him he can easily get past him.
Riddick doesn't have great long speed, running just a 4.68-second 40-yard dash (via NFL.com), and therefore won't be a great open-field threat in the NFL. It won't help that his backup, Cierre Wood, put up better numbers across the board at their Pro Day. Via Tylicki:
Riddick was never the feature back in college. He split carries with Cierre Wood his senior year, though he did have the yards advantage, 917 to 742. He also does not possess breakaway speed.
For a running back, he does not have a good build, which is leaner than preferred. While he makes up for it in toughness, he will need to bulk up to hang with NFL defenses.
Notably, he was able to perform at parts of his combine due to injury, but his pro day numbers were disappointing. A 40-yard time over 4.6 seconds and Wood easily beating him in everything could be cause for concern.
Overall, Riddick ranks as the 16th-best running back in the 2013 NFL draft class.
Drafted: Round 6, Pick 199, Detroit Lions