Emmanuel Sanders experienced a jolt in his career after leaving Pittsburgh
It has been a long time since the Steelers seemed to have a semblance of an effective offense. Back when Ben Roethlisberger was in his prime and the offense had a loaded room of weapons on offense that could attack any defense. Mike Wallace, Hines Ward, Antonio Brown, Heath Miller, and Emmanuel Sanders would line up on the field to try and score points for Pittsburgh.
As time went on and the top receivers on the team started to grow their portfolio, success and the need for the ball grew. There were not enough passing plays called to make everyone happy and that is when decisions started needing to be made. After three years of being anywhere from the second to fourth receiver option on offense, Sanders had enough.
The Steelers decided to move in a different direction and try to focus on keeping both Wallace and Brown as the main targets. That was not the worst decision made by the club initially, but it did have negative connotations when Wallace left for Miami via free agency. This divorce was not terrible for either side as Brown become a Hall of Fame caliber player on the field and Sanders would elevate his career elsewhere.
Perhaps keeping Sanders around and letting Wallace go would have been the right call in retrospect. Sanders was able to have a longer career and stayed affective for the most part throughout. Overall, moving on from Sanders was probably the best choice as it gave Brown the best opportunity to grow as a player in a bigger role on offense.