NFL Running Back Production By Years Of Experience

What exactly is the optimal years of experience for an NFL running back from a statistical standpoint? Based on the 2010 season, 3rd year running backs appear to be running away with that distinction, scoring 137 touchdowns (receiving TDs included). 2nd year backs scored 62 TDs, while 4th year backs scored 41 TDs. 3rd year backs totaled 21,365 total yards (rushing and receiving) while 4th year backs had only 7,284. It is possible that there was just an anomalously enormously talented draft class in 2008, and a different analysis is required to measure actual year over year declines in production based on years of experience. Is it just an anomaly, or are 3rd year backs the peak of production? When you look at the data and graph below, that surely looks too significant to be anomalous. Note that I did include QBs in my rushing data set, which only has a minimal effect on the statistics.

There was no correlation between career games played and change in yards per rushing attempt, and there was a much stronger relationship between declining rushing attempts per game and career games played. Ergo: number of carries declines more reliably that yards per carry. The point where carries per game began to decline (ie where the slope of the regression line intersects the X-axis) was after 61 career games played. 61 divided by 16 games per season is 3.8. Typically carries begin to decline in year 4, unless the back spent all or part of his first 3 years sitting on the bench waiting for a chance to play significant downs.

Heads up: Players entering 3rd season, Arian Foster, LeSean McCoy, Knowshon Moreno, Shonn Greene
Warning: Players entering 4th season, Chris Johnson, Ray Rice, Rashard Mendenhall, Matt Forte

	NFL Running Backs 2010
years	touches	yards	TDs
1	1367	6364	41
2	2096	11049	62
3	4188	21365	137
4	1569	7284	41
5	976	4507	23
6	1427	6577	37
7	951	4271	24
8	140	597	7
9	446	1869	15
10	536	2483	13
11	283	1244	6