You ask, how often does a player at UK leave early for the NFL? First. you give an incomplete list- I am not going to try to list every player, but I can think of one off the top of my head that you didn't list, Braylon Heard. Whether he should have left early or not is not the issue, but there are more players that have left early than you listed. A better question is, how often does an Alabama, or LSU player, leave early for the NFL? Several Alabama players do it every year, several LSU players do it every year, and Young is more comparable to an Alabama/LSU recruit than a typical UK recruit. As a matter of fact, Young is ranked higher than the vast majority of Alabama/LSU recruits. As far as UK recruits go, he is much more comparable to Couch, D. Johnson, and Robertson, than he is to Elam, Boyd, Barker, and Miller.
I am not saying that we should play Young out of a fear that he might leave early. I am saying, if he can significantly help this team, THIS YEAR, and only if he can do so, and if it's best for him in his own development, then the coaches will do so, rather than plan for a fifth year that may never happen anyway. Again, neither you nor I is in position to make this decision; I guarantee you that Stoops and his staff are going to consider every possible variable and make what they believe to be the right decision. If that's to redshirt Young, you won't hear a single complaint from me.