C.J. Spiller ran the 40-yard dash in 4.27 seconds at the 2010 NFL Combine. This is one of the fastest times ever recorded. Spiller weighed 196 pounds when he achieved this feat. Fast forward to the 2018 Combine, in which Saquon Barkley ran the 40 in 4.4 seconds, and one may question which time is better. Although not as fast as Spiller’s, Barkley’s time might be more impressive. Why? Because he weighed 37 pounds more than Spiller when recording it. Naturally, it’s alluring when a large RB prospect can keep up with his more streamlined counterparts.
In 2008, Football Outsiders created an equation to help us compare the 40 times posted by RBs of various sizes in what they called “Speed Score.” The equation is straightforward and calculated by multiplying a back’s weight by 200 and dividing this result by his 40 time set to the fourth power.1
While impressive, Spiller’s speed score of 118 is trumped by Barkley’s 124. In fact, using a data set that goes back to 1987, only two RBs have done better. Keith Marshall posted an absurd speed score of 127 in 2016 by running the 40 in 4.31 seconds at a weight of 219 pounds. Mario Fannin, a 2011 prospect, posted a time of 4.37 seconds while weighing in at 231 pounds, good for a speed score of 127.
Barkley’s score of 124, tied for third place with Knile Davis, Ben Tate, and Brandon Jacobs. As highlighted by these names, a strong speed score doesn’t guarantee success. It does, however, give us a way in which can compare the mixture of size/speed that RB prospects possess. The 2018 class did well with six backs finishing in the 90th percentile.
2018 RB Speed Scores and Historical Percentiles2
40 Time versus Weight
The scatter plot illustrates how, in general, 40 times increase as player weight increases. However, there are a number of players such as Kalen Ballage, Nick Chubb, and Derrius Guice that manage to plot in the lower half of the scatter and toward the right. If you’re looking for size/speed specimens, this is where you’d want to focus.
As expected, Barkley truly separates himself from the pack. As does Nyheim Hines. Although he’s lighter than the majority of the 2018 class, his 40 time of 4.38 differentiated him from the smaller backs. Like many things in life, it’s all relative.