Donte Whitner has said that he will appeal against a $21,000 (£13,000) fine for unnecessary roughness.
The San Francisco 49ers safety was penalised for a hit on St Louis Rams wide receiver Chris Givens during their game last Thursday.
The 28-year-old told the team's website: "I'm not happy with it. Still in my heart I feel like it was legal. 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. I can appeal it and see what they say.
"I say that because any big hit nowadays, whether you lead with the crown of your helmet, whether it's college football, they're all making that call based on how the hit looks, not on a guy lowering his head and connecting on the crown of his helmet."
Whitner has made 22 tackles and one interception so far this season.
