Whitner hit Rams wide receiver Chris Givens in the fourth quarter of the Niners' 35-11 victory. The hit dislodged the ball and prevented a Rams touchdown.
Whitner's penalty set up the Rams' only touchdown in the game.
Whitner says he will appeal and see if the league will lower the amount. He has 20 tackles and one interception for San Francisco (2-2) this season.
“I’m not happy with it,” Whitner said to 49ers.com.
“Still in my heart I feel like it was legal,” Whitner added. “I can’t change the way I play, so we’ll see what happens.” "I was going to the midsection, where the ball is, with my shoulder. You could actually see me turn to lay off the head. If I would have run through the guy, then I think I would have actually deserved that."