From breakout rookies to the re-emergence of Peyton Manning, there have been plenty of surprises among NFL quarterbacks this season. The dirty little secret of quarterback analytics, however, is that most yearly performances are actually pretty predictable.
Ben Roethlisberger might be quarreling with his offensive coordinator. Eli Manning badly misses having Hakeem Nicks at full health. Cam Newton took half a season to get back to where he was in 2011. But even these headline generators are having years that fit cleanly into the pattern of seasons each has posted in the past. For individual players, Total QBR jumps around by an average of 12 points from season to season. And of quarterbacks who have started in both 2011 and 2012, a large majority have seen their numbers vary within a range that could easily be explained by chance.
But not all. A handful of quarterbacks are having confounding seasons, with numbers that have jumped or plunged so sharply that it's difficult to evaluate where they're heading -- especially if they seem to be improving, yet aren't clearly playing at a championship level. Suppose we look at the starters whose QBR increased or decreased the most from 2011 to 2012, and set aside the few where the news for 2013 is obviously good (like Drew Brees) or bad (like John Skelton). That leaves us with a group of five hard cases to crack, using all the advanced statistical tools at our disposal: