It's a vicious cycle.
Every year, dozens of juniors leave early for the NFL, depleting the rising senior class of top talent for the upcoming season.
It happened once again a few months ago as dozens of underclassmen saw the threat of a rookie salary cap and felt the need to cash in while the time was right.
There's still some talented players left in the senior class, but many of the elite players in the game have the letters JR next to their name.
Even though NFL scouting departments aren't technically "allowed" to scout underclassmen, you can bet scouts will be keeping mental notes of many of these junior players.
Here's a look at 50 juniors (five at each position) who are poised to have a big 2010 season.
Ten players who just missed the cut at each position:
QB - Blaine Gabbert (Missouri)
RB - Shane Vereen (Cal)
WR - DeAndre Brown (Southern Miss)
TE - Kavario Middleton (Washington)
OL - Matt Reynolds (BYU)
DE - Adrian Robinson (Temple)
DT - Derek Wolfe (Cincinnati)
LB - Chris Marve (Vanderbilt)
CB - Brandon Boykin (Georgia)
S - Kenny Tate (Maryland)