Kevin Durant wanted no part of exchanging playful banter with a courtside fan on Wednesday -- telling a man bluntly, "Shut the f*** up and sit down."
The interaction happened at some point during the Nets' game against the Mavericks at Barclays Center in Brooklyn ... when a fan urged Durant to score more points during a small break in play.
"Kevin!" the fan shouted while the NBA superstar was hunched over just feet away. "You've got to take this game over!"
Durant took about a millisecond to digest the comment -- before he unleashed a savage response.