Could it be that Drisk came in with such lofty rankings/expectations? From an outsiders point of view, Drisk seemed to use his legs on a consistent enough basis to remain a threat. Harris, otoh, just lacks any sort of confidence in there. I know FSU's front seven is very athletic, however FAU's, VAndy's etc are much more beatable, yet Harris just did not attempt to pressure a defense with his mobility. Going back to comparing the two...I think Drisk's shortfalls/results were magnified because he came in with such a high ceiling e.g. 'next TT, etc". Harris was probably not expected to develop for a few years, however he was thrust into action out of necessity. I thought he exceeded expectations when he played for the JD LY, but his confidence has certainly waned.
Actually, Brantley could be thrown in the conversation as well. UF has had a tough run with QBs since 2009.