As a quick refresher to those of you who have forgotten how this works (or to those who have never heard of "Running Back Success Rate" before), we judge each run on it's "success" as opposed to yardage gained to get a more accurate picture of how good a running back really is. For a run to be deemed "successful," it must gain at least 40% of the yardage needed to move the chains on 1st down, 60% on 2nd down, and 100% on 3rd and 4th down. This type of metric ignores big run outliers that can skew others like yards per carry averages and simple total yardage figures. Fittingly, we have the poster child for why this is a handy metric to start things off. Shonn Greene finished the year with 1850 total yards and a very solid 6.0 ypc average, yet when we look at his success rate numbers he only comes out with only a 57% rate (excel spreadsheet, 43kb).
There are a couple of interesting things we can take from his numbers:
- If you consider how many of his rushes were for 10+ yards, you'll see that a good 31% of his successful rushes were for very good yardage. This is why I say he's the poster child for big run outliers; his every down production numbers were iffy at times but if he got a hole he was gone.
- Going along with that, his least "successful" performance was actually against a pretty stout run D. Against Penn State, who would finish the season with the #8 rushing defense in the country, Greene managed only a 43% success rate but still ran for 117 yards. In that game he managed 3 runs of 10+ yards and 10 runs of 5+ yards, yet routinely struggled in obvious run/short yardage situations.
- That 117 was his second lowest total of the season. Indiana managed to hold him to "only" 115 yards, but he managed a much more respectable 57% percent success rate against a defense ranked near the bottom of the country (91st) against the run.
- His most productive game of the year was also one of his most successful: Against Wisconsin, Greene rushed for 217 yards and an outstanding 8.7 ypc average, both season highs. He also ran at a 64% success rate and, despite having runs of 52 and 34 yards that helped bump that ypc up to such ridiculous levels, he was also advancing the ball at a steady rate.
- Compare that to his 64% performance against South Carolina: Greene gained 121 yards with a sub par 4.2 ypc average and didn't have a single run go for more than 11 yards (the only game he didn't last season), but he was very successful on 2nd and 3rd down (78% and 75%, respectively, his best "obvious run downs" performance of the season). The total yardage wasn't there, but it was still a solid performance in that he kept the offense and chains steadily moving.
- Amusingly, his most "successful" day came in the loss at Pitt. Greene carried for 147 yards and a 6.4 ypc average, both very solid numbers, and he also ran at a 70% success rate. Too bad the defense couldn't hold off Le'Sean McCoy.
Putting all of this together, we can get a picture of a boom or bust type of back. Obviously you want a back that can bust off big, game changing runs, but if you're going to be a feature back like Greene was for Iowa, breaking the big runs on 1st down while failing to consistently move the chains on 3rd and short isn't really what you want.
*note: I've worked this stuff up for a handful of top non-SEC backs, but mostly we'll be comparing backs in our own league. just an fyi.