When he found out that his beloved Washington Redskins clobbered the Dallas Cowboys 35-7 on Sunday, Armstrong grabbed a microphone before Sunday night's home game against the Minnesota Timberwolves and shouted "How 'bout those Redskins!"
The move is going to cost him $1,000 US.
With Armstrong in disbelief, Dallas coach Avery Johnson announced the fine during his post-game news conference. Team owner Mark Cuban later verified its legitimacy.
Mavericks' Darrell Armstrong is fined for his public pro-Redskins remark. (AP File Photo)
Johnson said the money will go to charity and the Cowboys would decide the recipient.
The ill-timed remark came during pre-game ceremonies, after guard Devon Harris wished the crowd at the American Airlines Center a happy holiday.
Despite not being scheduled to speak, the 37-year-old Armstrong asked for the microphone. He added his holiday wishes and then made the homage to his favourite NFL team.
Some fans laughed while others booed. Even Cuban was amused and joked with Armstrong when he returned to the bench.
with files from Associated Press
