It’s now up at Grantland:
The key to the 49ers’ success in that game, as well as for much of the past two years, is rooted in a common misconception about their defense. It’s often noted that the 49ers play almost entirely with two safeties deep, splitting the field into halves while the remaining defenders play man-to-man coverage. This tactic, which also relies heavily on the front seven to stop the run, is known as “Cover 2 Man” defense. The notion that the 49ers use this coverage almost exclusively is, like most misconceptions, rooted in some fact. The 49ers do use this coverage a great deal, but if they used it on every down, San Francisco’s defense would be much easier to attack than it actually is.
What Fangio and the 49ers actually do is mix and match their two-deep, Cover 2 Man coverage with a variety of “pattern match” zones — zone defenses that transform into a kind of man coverage after the snap. The 49ers use a variety of these pattern-match schemes (each of which is differentiated by a subtle change in a defender’s rules), but one I’ve seen them use with success all season is known to many coaches as “Two Read.
Read the whole thing.