There was a time, not so long ago, when the general wisdom was that it took skill position players three years of development before a team could really see what it had gotten in a draft pick. This was true of defensive ends, wide receivers, corner backs, tight ends and quarterbacks. The concept behind this, was that the talent level coming from the college game to the professionals was both a huge jump in level of competition and complexity of the playbook. It took young players the time to develop the skills and knowledge required to be playmakers.
However, the common expectations of have changed.