The process of selecting players for the NFL Draft is about much more than simply the game film and workout metrics. It's a complex rubric of numbers and information and character studies and just plain guessing trying to determine which 21-year-olds are going to morph into mature adults and contributing football players.

Each organization must come to terms with its review of a prospect's character and attitude and try to project how he will adapt and develop on and off the field. Players with drug or alcohol issues or criminal records in many cases require the authorization of an owner for them to remain on a draft board, and these selections involve myriad sources of information from coaches to trainers to doctors to advisers and family members.

So much of it is inexact and intricate. But what if this were an exercise in football acumen only? What if it simply came down to those who had proven themselves to be the best college football players in the country based on their production, skill and athletic testing?

In an attempt to sort that out I approached a noted evaluator I trust to create a few tiers of the best football players available. Again, this is strictly accounting for ability only and not incorporating injury history, off-field red flags, etc. This evaluator broke the prospects into tiers -- not necessarily listing them in order within a tier, but trying to determine those with true blue chip-talent, then the corresponding groups below.

We ended up with seven players in each cluster, and in essence tried to rank the top 20 players available, in his estimation (we ended up with 21 because, well, three times seven is 21 after all). Now, this won't be how the draft plays out, because those off-field issues are very real in many cases and there are obvious concerns with many of these players that will cause their stock to fall. But it will be interesting to look back on this exercise in a few years and see how it plays out, and how many of these players who don't go in the actual top 20 of the draft end up out-performing those who did, particularly should they mitigate the health or off-field concerns that are currently working against them.

Here's the breakdown:

Top tier: True blue-chip players

Myles Garrett, DE, Texas A&M: He's going first overall to the Browns for a reason.

Solomon Thomas, DE, Stanford: He might fall a little bit (by that I mean out of the top five) as he's probably best a 3-4 scheme fit, but there's a lot of natural pass rush to like about him.

O.J. Howard, TE, Alabama: The best of a deep and talented crop of tight ends.

O.J. Howard is the draft's best tight end. USATSI

Jamal Adams, S, LSU: The best of a deep and talented crop of safeties. Could toggle between free and strong as a play-maker on either side.

Leonard Fournette, RB, LSU: Has a chance to make a Ezekiel Elliott-type of impact from Day 1.

Reuben Foster, LB, Alabama: Tackling machine with a violent streak. Teams seem to be more comfortable with his off-field stuff as the process plays out.

Joe Mixon, RB, Oklahoma: The video of him striking a female is the biggest off-field story in this draft, but I don't see him getting past the Jaguars at the top of Round 2 (assuming they don't take Fournette in the first round). If the Jaguars do take Fournette, Mixon is gone by pick 48 (Vikings) or 50 (Bengals).

Joe Mixon is a top-tier player on talent alone. USATSI

Tier II: Grading out slightly lower

Jonathan Allen, DT, Alabama: I could see him going as high as third overall. Very clean player other than an injury issue last season. Hugely productive in SEC.

Jarrad Davis, LB, Florida: Likely to be the next LB to go after Foster is selected. At worst I don't think he slips past the Raiders at 24.

Jarrad Davis is the next-best thing after Reuben Foster. Getty Images

Tim Williams, OLB, Alabama: Has the pure speed off the edge people covet, but also carries a dossier of off-field stuff teams need to sort through. Has helped himself through this process however, and plenty of teams in the first round are comfortable enough to take him.

Marlon Humphrey, CB, Alabama: If you haven't noticed yet, my guy loves this group of Crimson Tide players. Humphrey is a first-round corner for sure, but other scouts I've chatted with might have him rated a tick lower. Time will tell.

Malik Hooker, S, Ohio State: If he had been a two-year starter, I suspect he would be in the top tier. He might not go quite as high as some originally projected.

David Njoku, TE, Miami (Fla.): Freakish athletic ability and unlimited potential. Raw, but teams love him.

Garett Bolles, T, Utah: The fact he's already in his mid-20s is working against him on some boards. Was a little surprised to see him as the first offensive lineman this evaluator liked.

Garett Bolles has separated from the tackle class, according to one evaluator. USATSI

Tier III: Other worthy top-20 selections

Gareon Conley, CB, Ohio State: Super clean and rising up draft boards because he has been a very productive two-year starter with no off-field or injury concerns. Is all football.

Dalvin Cook, RB, FSU: Has not helped himself with teams at all during this process, which he came into under heavy scrutiny. But he tore it up on Saturdays, no doubt about that.

Dalvin Cook's tape shows what he can do on a football field.  USATSI

Adoree' Jackson, CB, USCHas elite return skills that will help bolster his rise. In a perfect world he would be an inch or two taller.

Derek Barnett, DE, Tennessee: Highly productive off the edge his entire career in the SEC, though he lacks the ideal length.

Obi Melifonwu, S, UConn: Amid all the safeties getting all the hype, this could be the surprise guy (a la fellow Huskies DB Byron Jones two years ago). Incredible metrics (runs a 4.4 at 6-feet-4, 224 pounds) drawing plenty of quiet attention from scouting community.

Melifonwu is a name to watch on draft day. USATSI

Haason Reddick, LB, Temple: Former walk-on had a massive year for the Owls. If he was bigger, he might be better suited to the edge in the pro game, but should easily slide inside if need be.

Ryan Ramcyzk, T, Wisconsin: In a very weak crop of tackles after mauling in the Big Ten. Had been some concern as to whether he's a RT, but teams I talk to believe he is a LT in the NFL.

So that was his list. Interesting, but not surprising, that no QB merited strictly football consideration for him (his top passer was North Carolina's Mitch Trubisky, who would have been in a fourth tier). But we all know at least four will be drafted in the first round based on supply and demand as well as need. No receivers in this list, either, though Mike Williams of Clemson would have been in the next cluster of seven players, too.