Introducing running back success rate
This year I’ve used PPF’s extensive and detailed play-by-play rushing data to view running back efficient through a couple of different lenses. First, we adjusted every running back carry for the defensive front faced, then we did the same for down & distance. While both provided additional insight that isn’t readily apparent in the traditional yard-per-carry (YPC) metric, they shared a potential distortion with YPC: skewing results positively based on a small number of long carries. When the typical running back carry is only 3 or 4 yards, one rush of 80, 50 or even 25 yards will have a dramatic effect on averages.
This analysis is focused on finding running backs who are consistently getting at least the typical number of yards on their carries. I’m calling this metric success rate. There are a couple other definitions for success rate out there: numberFire sets the success bar at a positive contribution to net expected points (NEP), and Football Outsiders uses the percentage of yards needed by down. I think both measures have their merits, but I also believe they might unfairly penalize running backs for what’s out of there control, like running from a field position of low NEP leverage, or consistently running from longer down & distances.
My baseline for success looks at each running back’s individual carries and measures whether it is equal to or exceeds the median yards gained across the league at the same down & distance. I didn’t use average yards gained in order to minimize the effect of longer runs – the overarching goal of the analysis. While most down & distances have a median yards gained of three, the range might be wider than you’d expect. On 3rd and 1 the median yards gained was two, while on 3rd and 8 the median yards gained was eight.
Now let’s look through the year-to-date data and see if we can find some running backs whose YPC might be painting a rosier, or more pessimistic picture than their actual rushing success.