Frank Gore has been handed a $10,500 (£6,630) fine for a uniform violation during the NFC Championship game against the Atlanta Falcons on Sunday.
The 29-year-old told the Associated Press: "When you're playing, you don't think about it, you're trying to win. It's all good. I was wrong. Next time, I'll do better."
All NFL players are required to follow the league's strict rules on uniform during games.