In my ongoing quest to develop a projection system for offensive players in fantasy football, I examined the correlation between a running back’s offensive line and his fantasy production from rushing yards. Then, I examined the correlation between total fantasy points obtained from rush attempts and offensive line play. I have not included fantasy points running backs accrued from receptions because how well an offensive line performs at run blocking shouldn't impact a running back’s receiving prowess and production.
I have included data from the last three years and have used PFF’s rush block rating for each team to gauge the effectiveness of an offensive line’s run blocking. The average offensive line rush block rating from 2008-2010 was -2.8.
In our first sample, I included all running backs over the last three years who played in more than 40 total snaps. Because running backs with a small amount of carries would obviously have much fewer fantasy points than running backs with more carries, therefore skewing the results, I have used fantasy points per rush attempt to show the production of a running back. As an aside, the average fantasy points from rushing yards per attempt from 2008-2010 of this sample was 0.423753.
The x-axis (independent variable) is composed of offensive line rush ratings and the y-axis (dependent variable) has the fantasy points from rushing yards per attempt.
As you can see from the scatter plot, there is not a strong correlation between the effectiveness of an offensive line and the fantasy success of a running back. The correlation coefficient backs up our eyes as it reads .25 and is statistically significant with over 250 data points.
The data backs up what we see each year in fantasy. In some cases, a running back can succeed and run well with a poor offensive line, like LaGarrette Blount did in 2010. Tampa Bay’s offensive line was among the league’s worst this past season, grading out at -74.6. Despite that, Blount averaged .50095 fantasy points per attempt this season, an elite number, and propelled many fantasy teams to the playoffs. Other running backs that achieved fantasy success despite their offensive lines in 2010 include Adrian Peterson (-66.8 run block rating, .45 fantasy points from rushing/attempt), Chris Johnson (-95.6 run block rating, .43 fantasy points from rushing/attempt) and Matt Forte (-60.1 run block rating, .45 fantasy points from rushing/attempt).
Reggie Bush, however, was unable to make good use of his offensive line in 2008 (60.1 rush block rating) as he scored just .381132 fantasy points from rushing yards per attempt. Marion Barber also falls into this category with his 2010 season (51.7 run block rating, .330973 fantasy points per rush attempt).
In an attempt to double check my work, I ran the correlation again, but changed the threshold from 40 snaps to 100 rush attempts to include running backs who were regular contributors throughout the season.
Again we see the correlation between the quality of an offensive line and a running back’s production from rushing yards is weak with a coefficient of .23.
Just to check, I also ran correlations between offensive line rating and total fantasy points from rushing (so this set include fantasy points from touchdowns), and for our first data set (threshold 40 snaps) the correlation came out to .23 and when we increased the threshold to 100 carries the correlation increased to .29, both of which show there is little or weak correlation between the strength of an offensive line and the fantasy production of a running back.
Conclusion – How can we use this data to project running back success in future years? The answer is simple: don't worry about how strong a team's offensive line is when deciding what running backs to draft. Even during the season it's not important how well an offensive line is performing as far as your running backs are concerned. I know that during this season I often times checked how well an offensive was playing when ranking players and making recommendations, but as we can see from our data, it's not a very important factor.
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