The NFL is unlike every other sport, in that the short season doesn't allow much time for regression to really take hold. In the NBA, you have 82 games for a player's true talent level to take hold; in baseball, you have 162. Generally speaking, players will perform close to their talent level over the course of a season, even if the game-by-game results are all over the place.

That tends not to be the case in the NFL, where production varies wildly not just from game to game, but from season to season. Sometimes, you can identify a player for regression and that regression happens all at once -- look at Drew Brees' seven-touchdown game after starting the season slowly. Sometimes, however, a player can go an entire season under-performing his talent level without things turning around.