Thoughts on Ranking Prospects
Height, weight, 40 times, bench presses...these things don't tell you whether a man will be a good pro. What they do tell you is how well a player will be able to apply his skills at the next level. The physical attributes become sort of prerequisites to be able to do certain things on the field. With insufficient speed, a player who previously excelled at man-to-man coverage may not be able to keep up, so his skills wouldn't transfer as well to the NFL. But the higher level of competition also weeds out those who relied on athleticism instead of skill. The key to remember is that a man's physical limitations are just that; they tell you what a player cannot do, instead of what he can.
Play on the field should be the first and the last thing scouts look at. A workout warrior who didn't impress on the field is at best a raw prospect (if he has not been playing long enough to learn the nuances of a position). If a player has been in the game for a long time but still has not mastered the fundamentals of his position, doesn't seem to recognize how plays develop, struggles to learn a playbook, can't pick up what the coaches try to teach him, or has other major difficulties with the mental and technical aspects of the game--these aren't problems that are likely to go away. You look at what he has done on the field and only after that do you look at the workout numbers to see if it is likely he can repeat or improve on that in the pros. Again, the only exemption is for players who are still learning the position. In those cases, it is just harder all around to predict how successful they will be.
Senior Bowl performances largely tell you how well a player can be coached and how he stacks up when taken out of his normal scheme. A good Senior Bowl is a testament to a player's adaptability and skill against other top competitors, but the practices tend to tell more than the actual game. After all, the game is much like a Pro Bowl; the quarterbacks and receivers don't have chemistry, the linemen aren't always on the same page, etc.
Interviews are underrated by the average fan, probably because they are one element of the process we can't quantify or reliably gauge the effects of. However, this whole process is at its core a job application, and as with most job application processes, the interview can make or break a candidate's chances. Coaches and teams have to believe that the player's heart is in it, that he is motivated, that he works hard, that he is reliable and trustworthy. A player has to be mentally tough and driven to succeed in the NFL. Otherwise, hungrier players will beat him out. A reckless player can not only get himself suspended but tarnish the name of the franchise.
Other considerations include level of competition, the scheme played in, the ability of the coaching staff (are his mistakes the kind that are easily correctable?), leadership/character, and to some degree image/marketability (this is a business after all).
All in all, I think the preferred draft prospect is a great college player with good workout numbers, preferably from one of the tougher conferences (i.e. SEC, Big 12, Big 10, Pac 10, ACC).