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 3rd-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.
In 2011, Donald Brown posted the best yards per carry for any Indianapolis Colts running back in years. Brown was drafted to be a "home-run hitter," and to provide a contrast to the more plodding Joseph Addai.
As the Colts line improved last year, Brown showed off that big-play skill. However, his success rate was terrible.
Success rate was the hallmark of an efficient Colts offense for years. The Colts did not always have a great running game, but they had an effective one.
Peyton Manning was the master of calling the right play at the right time. If the Colts needed three yards, Manning would call a play that got three yards. The result is that the Colts running backs were perpetually in the top 10 or top five in the league in success rate.
From 2005-06, the Edgerrin James and Addai both led the league in the stat. Even during some of the bleakest years of running the ball, like 2008, the Colts still fared well in success rate.
Last year, despite the best yards-per-carry mark from a Colt since 1998, Brown was only 49th in success rate. Brown had 16 carries account for more than half his total yards in 2011. On his other 118 carries, he averaged 2.68 yards.
That's in line with numbers from Arian Foster and still vastly superior to Chris Johnson. Brown is clearly a boom/bust runner, which is what he was drafted to be. Still, one has to believe that had Manning been his quarterback, he would have posted success rate numbers in the mid-40s as he had his first two years in the league.