When players leave one team and head to a new one via free agency, the acclimation process has to be challenging. Based on the position someone plays, it can be even more challenging.
As an example, if a defensive lineman is signed he has to worry about those who are playing alongside of him, but it ultimately comes down to him doing his job and beating the man in front of him. However, at a position like wide receiver, you have to worry about the person throwing you the football. After all, a receiver can’t throw himself the ball, despite many suggesting this is an option.