The NFL has done a lot of work to take out the kind of body-bag hits that used to happen from time to time. If you look back through the lore of the NFL, members of the Pittsburgh Steelers’ have been at the forefront of some of the rule changes. There was the Mel Blount rule in the late 1970s to stop cornerbacks from mugging wide receivers. The Hines Ward rule in 2009 to prevent crackback blocks. And then finally a rule inspired partially by James Harrison in 2010 to prevent helmet-to-helmet contact and big hits on quarterbacks.
There were many big hits that Harrison delivered throughout his career, but one that instantly comes to mind is his crushing blow to Cleveland Browns WR Mohamed Massaquoi.