Feast your eyes on a Bills Mafia member who bungled a table-smashing effort so badly on Monday -- he ended up nearly breaking bones in his lower body!!

The terrifying/hilarious scene all went down in a parking lot tailgate near Highmark Stadium in Orchard Park just hours before the Bills took on the Patriots.

For some reason, a fan decided to climb on top of a bus to break some dining room furniture before the big AFC East showdown -- but, unfortunately for him, it didn't go so well.

Watch the clip -- as fans gassed up the Bills backer (who was dressed in Buffalo gear and, thankfully, a helmet), the dude jumped ... and, well, he didn't stick the landing.

The guy missed the table almost completely -- crashing down on HARD on his tailbone.

A witness, though, tells us somehow the guy avoided serious injury -- but he was moving around gingerly and was clearly sore.

To make matters worse, the guy's night didn't get much better after that ... 'cause the Bills went on to lose a bad one to the Patriots, 14-10.