2012 Field Position Margin
That play and a question from @squick4n regarding the St. Louis Rams' average starting field position led to this finding: San Francisco and Seattle lead the NFL in average field position margin. The margin reflects the difference between where their drives begin and where their opponents' drives begin, on average.
The Rams rank 30th in this category.
Arizona ranks ninth after beginning two drives at the Detroit 5-yard line or closer during a 38-10 victory Sunday. The Lions began three drives inside their own 10.
A combination of kicking, punting, special-teams coverage, turnovers and turnovers forced will influence the averages.
This will be one angle to watch when the 49ers and Seahawks play in Week 16. Seattle's average drive start against the 49ers in Week 7 was its own 15-yard line, the worst average start for any team in a game to that point in the season.