Harkey was rather unheralded for much of his career at UCLA, where he only had one pass thrown his way as a senior and was used mostly as an extra blocker. He has good size as a blocker, but it is unlikely he will work upfield much as a pass catcher in the NFL.
Harkey is an effective blocker in the running game and uses his frame and hand technique to make a difference. Other than working to seal blocks on the edge, Harkey hasn't shown enough other skills that project at the next level, other than being able to move on his large frame.
As a pass catcher, he isn't a mismatch. Although he's much bigger than most safeties, he isn't faster than them, and that will be his main problem. Being targeted only once in an underperforming UCLA offense is not very attractive to NFL teams. Harkey truggles to work off defensive ends and get into his routes, and he can't separate from defenders. He will be considered a glorified sixth lineman in the NFL, if that.
Future Hall of Famer
A once-in-a-generation type prospect who could change how his position is played
An impact player with the ability/intangibles to become a Pro Bowl player. Expect to start immediately except in a unique situation (i.e. behind a veteran starter).
A quality player who will contribute to the team early on and is expected to develop into a starter. A reliable player who brings value to the position.
A prospect with the ability to make team as a backup/role player. Needs to be a special teams contributor at applicable positions. Players in the high range of this category might have long-term potential.
A player with solid measurables, intangibles, college achievements, or a developing skill that warrants an opportunity in an NFL camp. In the right situation, he could earn a place on a 53-man roster, but most likely will be a practice squad player or a camp body.