Success rate is a simple metric that attempts to put a number on the difference between those plays - one of those plays is a successful one (it gained a first down), the other is not.
Your definition of success may differ from mine, but I've opted to define a successful running play as follows:
1) On first down, it gained at least 50% of the needed yards.
2) On second or third down, it gained 100% of the needed yards.
3) The runner did not fumble on the play.
In other words, a 5 yards on 1st and 10 is successful, but 5 yards on 2nd and 10 is not, and neither is a 15 yard run on 1st and 10 where the runner fumbled after gaining the yardage. Possession of the fumble is not relevant, any fumble, recovered by the offense or not, is considered to be an unsuccessful play. (Ask any coach and I think you'd find they agree.)
Success rate is shown as a percentage (successes / total attempts). A rusher with a high yardage total and low success rate probably tends to have long runs mixed with frequent stops for short or no yardage. A rusher with a low yardage total and high success rate is getting just enough to be successful, and not much more (perhaps indicative of a goal line QB or full back).
2014 Success Rates through Week 5
Through week 5 I've limited this list to running backs with at least 15 carries, and quarterbacks to those with at least 5 carries. I will increase these value as the season goes on.
|Success Rate - Running Backs (min 15 attempts)|
|Success Rate - Quarterbacks (min 5 attempts)|
By itself, Success Rate doesn't tell the whole story about a runner (would anyone rather have Pat White's 100% success rate and 1.7 YPC than Tanner Marsh's 88% and 6.4 YPC?), but it does provide an interesting metric to add to the conversation.
2013 Success Rates
I intend to put up a page on cflstats.ca to display success rates for all seasons, but in the meantime, here are the values for last year.
|Success Rate - Running Backs (minimum 50 attempts)|
|Success Rate - Quarterbacks (minimum 15 attempts)|