On the surface, his numbers are terrific. The only problem is that they don't lead to wins.
This week, Advanced Stat of the Week will look at running back success rate. Success rate is one of the most important ways to judge the true effectiveness of a runner. Consider the following hypothetical runners.
Runner A has one 80-yard carry and nine carries for no gain. His stats are 80 yards, 10.0 yards per carry.
Runner B has eight 10-yard carries. Two of his carries came on third and 15. His stats are 80 yards, 10.0 yards per carry.
Runner C has 20 carries, for four yards each, but all his carries came on 3rd-and-3 or less. His stats are 80 yards, 4.0 yards per carry.
The back who helped his team win was the back with the fewest yards per carry, but the most successful runs.
Success rate illustrates that a runner's ability to move the chains is his most important quality. "Boom and Bust" backs can be exciting, but carries for negative yards are drive killers. Long runs thrill fans, but consistent gains are more valuable.
The Football Outsiders calculate success rate roughly in terms of the percentage of yards gained by the runner each down. On first down, a back needs 40 percent of the yards his team needs for a first down. On second down, that jumps to 50 percent. On third and fourth down, a run is only successful if the back gets 100 percent of the necessary yards.
In terms of success rate, a three-yard run on 1st-and-10 is not successful. A three-yard run on 2nd-and-5 is successful. An eight-yard run on 3rd-and-10 is not successful. This sliding scale helps account for meaningless yards that a back accrues during the course of the game. Seven-yard gains on a draw on 4th-and-20 don't often mean much in the course of a football game, and Success Rate shows us that. A running back should be looking for a success rate north of 50 percent.
As noted before the season, success rate has long been a problem for Chris Johnson.
Sure enough, he repeated his 2011 performance perfectly. His success rate was still mired at 41 percent, worse than more than 30 other running backs.
His inconsistency continues to be a problem. Offenses thrive on predictability of performance, and Johnson simply doesn't offer it.
If there is a silver lining for the pro-CJ crowd, it comes from his percentage of runs gaining over 10 yards. While still lagging behind his early seasons, Johnson was able to hit big gains more often in 2012 than in 2011. His yards per carry on those gains was up as well, illustrating that he still has home run burst.
Johnson continues to be one of the most frustrating offensive players in football. He's undeniably talented and can be thrilling to watch. No one questions that he has value and a role in a successful offense.
Unfortunately, that role may not be lead back. Given the nature of his performance, it's safe to wonder if he might not truly thrive in a two-back set where another runner can take some of the carries.