The physical nature of the NFL wasn't restricted only to the gridiron this weekend when the San Francisco 49ers visited the Arizona Cardinals - as a pretty disturbing video that has emerged today proves.
The video (below) shows fans of both franchises getting into an altercation high in the stands at the University of Phoenix stadium which quickly escalates into an all out brawl in which women are sent flying over their seats, punches are thrown and (a lot) blood is spilt after those involved tumble down the concrete staircase.
Be warned: It doesn't make particularly pretty viewing.
Security guards do attempt to bring control to the situation but by the time they arrive there is little they can do to stop the melee - and in fact the guy in the blue shirt ends up with more blood on him than most of the fans.
Hopefully no one was seriously hurt and judging by the level of violence some of the fans involved are looking at some big time punishment ahead.
Sometimes it is just better to watch the game at home.
The game itself
It isn't clear in the video as to what stage the game is at when the fight breaks out, but with the 49ers and Cardinals players playing out a close 23-14 (in Arizona's favor) game it's safe to say that tension was high throughout the afternoon game.
Add to that the fact that Jim Harbaugh's team blew a lead for the second consecutive week, plus the age old tradition of tailgating which as we all know involves its fair share of alcohol, and it probably didn't take much to light the torch paper between the two sets of fans.
One of the great things about the NFL is that - unlike fans in soccer's English Premier League who are separated by security and police - travelling fans and home fans can sit side by side to watch their respective teams compete in arenas and stadiums up and down the country.
Scenes like this however are likely to get people talking about just how sensible that is.
Having said that with the Cardinals' stadium boasting a capacity of 63,400 the idiots in the video above really are in the minority.
After weeks of off-the-field controversy involving its players the NFL certainly won't enjoy seeing scenes such as these from their fan base however.