One of the things that NFL Teams watch for are players that have dominated college football, but will flop in the NFL. This may seem strange that players that dominate college would fail in the pros, but it really should not be surprising for a few reasons.
1. Elite Coaching
One of the reasons that college players can dominate is due to superior coaching. When players at the college level have better coaching and thus superior technique (even if they are similiar athletically), they often dominate. Programs like Alabama are able to remain competitive because they both recruit and coach well. This allows them to coach up their 3 and 4 star prospects to perform on the field as 4 and 5 star prospects. However, once these prospects reach the NFL, they now face opponents with equal coaching and often equal or better athleticism. Essentially, these prospects have reached their total potential at the college level.
2. Speed of the Game
Some players rely on sheer effort or strength to make plays. At the college level they are able to overcome speed deficiency, through hustle and/or strength. The reason that they are able to do this at the college level is due to the reduced speed of the game (vs. NFL) and diversity of skill amongst competition. The perfect example of this would be Tim Tebow, QB, Florida, a College quarterback who dominated through overpowering strength and determination. However, at the NFL level linebackers are just as big if not bigger, stronger and faster than the college level. Tebow was no longer to outrun linebackers to get the edge or overpower them up the middle.
3. Single Dominant Trait
Some players at the college level dominate because they have a single dominant trait. This is very common among skill-position players, especially wide receivers. A wide receiver may have exceptional speed, size, or route running ability, however that does not necessary translate to a successful NFL career. Reggie Williams, WR, University of Washington, he was a dominant player at WR (Consensus All-American) primarily because of his physical stature. Williams was an imposing 6’4″ and 200lbs+, obviously a mismatch for many of the corners he faced.
4. Outstanding Supporting Cast
This is most common at the quarterback position, but can also be true at any position. Some players just dominate college because there supporting cast is so good, that they are put in a position to succeed even if they only play okay. Occasionally, they are positioned the opposite of incredible talent and rack up stats because they are the weaker opponent for the offense to attach.
Matt Leinart, QB, USC was a perfect example of a player who succeeded only because he was surrounded by an outstanding supporting cast. In 2004, Leinart played with Steve Smith (NYG in 2009, had 1000+ receiving yards), Dwayne Jarret (All-American and 2nd Round Pick), Reggie Bush (Heisman Winner, 2nd Overall Pick, 2 x 1000+ rush yards seasons), LenDale White (2nd Round Pick, Winston Justice (2nd Round Pick), Ryan Kalil (All-Pro Centre), Sam Baker (1st Round Pick), Fred Davis (2nd Round Pick), Sedrick Ellis (1st Round Draft Pick), Lawrence Jackson (1st Round Pick), Keith Rivers (1st Round Pick), Lofa Tatupu (All-Pro, 2nd Round Pick, All-American), Keith Rivers (1st Round Pick, All-American).