I was also curious about the consequences of entering the draft early. This is all that I could find online:
NFL Draft Advisory Board
College football players who are considering entering the NFL draft but who still have eligibility to play college football can request an expert opinion from the NFL-created Draft Advisory Board. The Board, composed of scouting experts and team executives, makes a prediction as to the likely round in which a player would be drafted. This information, which has proved to be fairly accurate, can help college players determine whether to enter the draft or to continue playing and improving at the college level. There are also many famous reporting scouts, such as Mel Kiper Jr.
The NFL Draft Advisory Board (sometimes initialized as the NFLDAB) is a panel of professional football scouting experts who offer advisory opinions to college football players as to the likely level of demand for the players' services during the NFL draft.
The board was created in 1994 to assist those college football players who were eligible to continue playing NCAA football or enter the NFL draft. Although the NFL had begun permitting such "underclassmen" to apply for the draft in 1989, within a few years it was clear that commission-based sports agents had deluded many of them as to their likely demand by teams and future salaries. 76 of the first 165 underclassmen to apply were not drafted, and once a college football player has entered the draft, he is no longer eligible to play college football. Thus, it was important that such players understand whether they would likely be among the small number of players drafted, and what their salaries might be, before committing to the process.
