NEW YORK, January 21, 2010 (AFP) - Boston Celtics forward Glen "Big Baby" Davis was fined $25,000 by the NBA on Thursday for directing inappropriate language at a fan during a game at Detroit on Wednesday.

NBA executive vice president of operations Stu Jackson announced the fine, for language Davis used toward a fan in the second quarter of Boston's 92-86 loss to the Pistons.

A jeering fan called Davis a "fat boy" and told him to lose some weight. Davis responded with an expletive.

"We know what happened, and that's unacceptable," Celtics coach Doc Rivers said after the game. "It's tough when the fans are yelling that stuff at you, but you have to be stronger than that."

Davis was the second Celtics player to be fined in as many days. Boston forward Rasheed Wallace was fined $35,000 on Wednesday for criticizing officials.