Guys like Jadeveon Clowney, or Jerry Hughes - guys that played on the line in college, but are fast enough to play a sort of hybrid LB/DE position. Essentially, they're big, strong, and insanely fast.

Most college teams don't have access to those guys (or don't have enough of them to effectively run the scheme). Their LBs are generally either big or fast... but they rarely get guys that are both.

A successful NFL scheme doesn't necessarily translate to college success (just like highly successful college schemes often don't catch on in the NFL).