Both players rank among the NFL leaders in penalties for unnecessary roughness, unsportsmanlike conduct and less specific personal fouls.
Their history dating to their NFC West days came to mind upon reading about Smith pulling off Incognito's helmet and swinging it at Incognito's head. Last season, the NFL fined Smith for kicking Incognito in retaliation for Incognito allegedly twisting Smith's ankle to inflict injury. These are the sorts of grudges we tend to enjoy reading about years later, after players are retired, even if their actions crossed lines. We're looking for evidence players were as emotionally invested as fans tend to be.
Of course, violating the rules isn't a requirement for emotional investment. Plenty of players go all out while avoiding the penalties outlined in the chart below. Six of the 10 players listed have NFC West ties. The penalty counts date to 2006, so the chart is biased to show longer-tenured players.
Filtering to show only the past two seasons only enhances the NFC West flavor as Dashon Goldson (10), Aaron Curry (six), Kam Chancellor (six), Breno Giacomini (six) and Brandon Browner (five) are among the eight players with more than four such penalties over that span. Incognito has four and Smith two.