Aside from size, one of the initial things to look for in a receiver is explosiveness. Receivers have to be able to surge off the line. If they can't, cornerbacks will easily smother them, and their timing with the quarterback will be thrown off.
The 2014 recruiting class has a ton of good receiver prospects, but several of them exhibit better explosiveness than others. These receivers can launch into their routes, immediately threaten secondaries and also have the ability to transfer upfield in a flash after the catch.
They will be exploding on a field near you soon.