From Mike Garafolo at NJ.com:
John Carney will kick his sixth game for the Giants today against San Francisco, according to someone with knowledge of the situation.
The person, who requested anonymity because he isn't authorized to speak for the team, said it's likely the reason is that Lawrence Tynes spoke over coach Tom Coughlin's head earlier this week when he said he would kick in today's game. Tynes is healthy after suffering a knee injury during the preseason.
The moral of the story? "Shut up and kick, I'll call you when I need you."