There seems to be some confusion. Suh wasn't signed to be a leader. He has never really taken that role anywhere. He was signed to break the opposing offense, for which he has proven exceedingly effective.
Still I can assure you that the coaches would love for him to embrace a leadership position on this team. There was an interview with him and the reporter asked Suh if he's ready to be leader (something along those lines) and Suh responded by saying that yes he's going to mentor and help the younger guys on the team and how different it is since he never had to embrace that role with the Lions.
I'll try to find the interview.