i remember readin and making thread on this topic
NFL's problem with underclassmen declaring for draft is getting bigger | The MMQB with Peter King
The reason that there has been such a rise in underclassmen declaring for the draft is because of the rookie wage scale instituted by the owners. All draft picks are now locked into their rookie contracts for at least three years. The impact on the first-round picks is even more punitive since teams hold an option for a fifth year, and then they can be franchised in the sixth..
NFL's problem with underclassmen declaring for draft is getting bigger | The MMQB with Peter King