What's the difference between these two situations?
1. On 1st and 10 from the opponent's 30, a RB gets a handoff and breaks free for a 30 yd TD.
2. On 1st and 10 from his own 30, a RB gets a handoff and breaks free for a 70 yd TD.
In both plays, the RB read the blocks and made the moves necessary to break into the open field. In both plays the RB's speed and agility beat the safeties. But the difference of 50 yds is basically statistical trash because in situation #1, the RB likely could have kept running for another 50 yds.
In rating running ability, I've previously suggested the use of median statistics rather than average statistics. When we want to know how good a team's running game is, or how good a RB is, we want to know the central tendency of the team or player. The statistical mean is only one way of looking at central tendency. Median can often be more useful. Averages are often distorted by a very few outlier inputs.
Consider this fictitious example examining the central tendency of college dropouts who live in Redmond, WA. Let's say there are 5,000 college dropouts in Redmond, Washington, and each make $30,000/yr except this one guy named Gates. He makes $20 billion/yr. The average salary of a college dropout in Redmond is over $4 million/yr. So if I'm a student in Redmond I should skip class tomorrow, right? $4 million/yr might be the average, but it's not the central tendency and it's virtually useless information.
Which player would you rather have on your team? A RB who gets at least 4 yds on every carry, or a RB who gets 29 1-yd runs and one 91-yd run? Both players average 4 yds/carry. The first player's median rush is 4 yds and the second player's is 1 yd. It's an extreme example, but it illustrates my point. Consistency has its value.
Here are a list of the top runners of 2006 sorted in order of their percentage of runs >4 yds. It's interesting to compare to their average yds/rush, their total yards, and other stats. (Ties are broken by % of carries > 3 yds.)
I'm not suggesting average rushing is worthless, just that it is only part of the story.