Sometimes in the NFL it isn't about how good somebody is, but about how bad. The biggest improvements can often by made by strengthening the weakest link on a team, by bringing in a player who can perform at a higher level, even if he isn't a Pro Bowl talent.
For a variety of reasons, the NFL is full of underachieving players. Sometimes injuries have robbed a player of the ability he once had, sometimes he has just quietly gotten too old and has yet to be replaced, and sometimes teams have just not been able to find somebody better. But in all cases, those players can be the difference between winning and losing.
The NFL is ruthless and smart enough that if your opposition finds a weakness, that is exactly what they are going to attack. Why try to run through a wall at its thickest point when you can focus your attention on the rickety wooden gate halfway along?
With that in mind, I'm going to look at 10 players who must be replaced in 2012.