Dallas Mavericks Fan Screams 'Fire Nico' In GM's Face Before Game

Dallas Mavericks fans clearly still loathe Nico Harrison for trading away Luka Doncic ... one actually yelled right in the GM's face on Monday, "Fire Nico!" -- repeatedly!

The scene unfolded just before the Mavs' tilt with the Brooklyn Nets at American Airlines Center in Dallas ... as Harrison -- who jettisoned Doncic to the Lakers back on Feb. 1 -- was saying hi to some people who had shown up for the game a bit early.

The 52-year-old shook one person's hand, and then as he turned to go back to Dallas' locker room area -- a Mavs backer yelled that he should be canned.

The fan screamed it three separate times -- getting louder with each yell.

To Harrison's credit, he didn't react, and walked into the bowels of the stadium without further issue.

But, according to one Reddit user who claimed to have seen the whole incident, stadium security confronted the fan a short time later. It's not clear if the guy -- who was wearing a No. 77 Doncic Mavericks jersey -- was removed from the venue over the altercation, though the officials didn't seem pleased with him, to say the least.

Harrison's Mavs, meanwhile, continued to struggle without Doncic -- they lost to Brooklyn, 113-109. They're now 37-39 in the year.