Dallas Mavericks Player Drills Fan In Head With Errant Pass During Game

An NBA fan didn't keep her head on a swivel while she was trying to take her courtside seat at a game on Tuesday night -- and she paid for it ... getting drilled in the noggin by an errant pass.

The painful moment happened just a few minutes into the Mavericks vs. Pelicans game in New Orleans ... when a woman had her back turned to the court as Dallas was trying to get a bucket on the floor.

Luka Doncic threw up a shot, missed, and when Dorian Finney-Smith grabbed the rebound -- he looked to kick the basketball out to one of his teammates.

The problem? His pass was tipped out of his hand -- and then it made a beeline for the unsuspecting woman's head.

The ball clanked off the back of her dome with some force ... but, fortunately, she appeared to be OK. Also, like a true champ, she didn't spill any of the water she was holding -- and laughed it all off.

Later in the game, retired NFL head coach Sean Payton showed off exactly how fans are supposed to handle themselves while courtside ... using some cat-like reflexes to nab a tipped ball that came his way before it did any harm.