The Bills' struggles on the field have apparently frustrated Buffalo fans so much, they've now turned on each other -- getting into a violent fistfight at the game on Monday night.
The wild scrap happened at some point during Buffalo's loss to Denver at Highmark Stadium ... when several fans clearly became upset with a man in a Josh Allen jersey.
It's unknown what sparked the commotion ... but you can see in video shot by someone a few rows away from it all, fists started to fly just seconds after words were exchanged.