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 San Francisco 49ers running back was judged to have worn his socks too low during the game that saw the side progress to the Super Bowl for the first time since the 1994 season.
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.
