Then it becomes a question of risk/reward. In this situation, a team is drafting in the 7th round with Burfict still on the board. Everyone knows that he can play and everyone knows the negatives on his record. The risk in this situation is relatively low. 7th round selections aren't generally expected to have a long-life in the NFL, and some fail to even make the team. But you have a player sitting there with the potential to contribute at a high level if only for a few years.
So lets say hypothetically, Burfict contributes at a very high level for 3 years, finishing each season among the top of the league in tackles and also helping lower the yardage per play while in the game (When Burfict was on field, the Bengals defense allowed fewer yards per play at 4.5 compared to 6.9 when he was off the field).
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Then in the offseason, he goes completely berserk and disappears in a jungle somewhere never to be seen again. Well, you still got 3 years of high productivity out of a 7th round selection. To me, those 3 years vastly outweigh a 7th rounder that gets no playing time at all and is out of football after one or two seasons of riding the bench.