The addition of Bill Callahan to the coaching staff of the Cleveland Browns, assuming it goes forward as planned, could be a major step forward to develop Cleveland players on the offensive line. Consider that no offensive lineman has developed into anything resembling a successful NFL player since Joel Bitonio was drafted in 2014.
Meantime the team could not re-sign Alex Mack and did not re-sign Mitchell Schwartz. Since leaving Cleveland, Mack has been on three Pro Bowl teams, and Schwartz made All-Pro in 2018. It would be fair to say that both players enhanced their careers after leaving the Browns.