One of the many reasons that the Pittsburgh Steelers prefer to build their roster through the draft is because you don’t know what a player is like when you bring him in from another NFL organization—especially if he isn’t someone whom you heavily scouted coming out of college.
We can see this in the Steelers’ spotty track record when it comes to acquiring players via trade, some of whom work out better than others. Sometimes that changes in perception from season to season, or even in-season. The latter was the case for Ahkello Witherspoon, who was picked up just before the regular season started.