Uh, TCU is a top-ranked D and Vernon shredded it. He also shredded PAC-12 D's. What more does this guy want? 
Vernon isn't a running threat, he's a scrambling one--- he never looks to run, he looks to complete passes downfield. With the proper WRs that keep running their routes, he could be just as devastating to NFL defenses as he was to TCUs and every other kind of scheme that tried to stop him.
A bonus: the kid has character, something top picks Manziel and Shameus Winston did not.