As somebody who studies the social functions and cultural context of language, I've always found it fascinating how often the game of football uses metaphors of and references to war. "The battle is won in the trenches" is a phrase that has found context since use by the Roman legions. We talk about straining for a short-yardage conversion as going "over the top", a term typified by World War I. Indeed, the use of "air raids", "road grading" (clearing the way for the "ground assault"), and, of course, the quarterback as "field general" is common in the NFL.
And, yet, if the quarterback is the "field general", it seems as though the running back has become the NFL's "cannon fodder".
Over the past decade, the NFL has increasingly become a pass-oriented league. Teams have even reduced the role of a running back from a "bell cow" (not a war metaphor) to a "specialist", reducing injury and veiling weaknesses in any one player. Even more so, the NFL has started leaning away from drafting running backs highly. From 1963 to 2012, no draft had gone by without at least one running back being selected in the first round. In 2013? Not a one. Now in the 2014 draft cycle, even the NFL College Advisory Committee, when awarding its top running back grade this year, handed Arizona's Ka'Deem Carey a second-round grade instead of a first.
I became curious: By waiting on running backs in the draft, are NFL teams actually saving themselves value? Or is this simply a draft day "Mexican standoff", in which teams are losing out on top talent at the position? I studied the careers of every running back drafted in the NFL Draft since 2000 to find out whether or not this "late-round running back" strategy worked for the NFL. For fans of every runner-needy team who are clamoring for Carey or Carlos Hyde in the first, you'll be interested to see the results.
A New Era
We know about the demise of the running back as an offensive focal point in the NFL. A decade ago, there were nine rushers who totaled over 300 carries in a season; this past year, there were just two. Teams are also less willing to pay running backs, deciding that they need not invest a lot of money into one player to do what a few players can do for much cheaper. It makes sense: why pay one "complete" back $13.7 million per year (2013 Vikings) when you can get a two-down back, a pass-catching back, and a goal-line back in total for a third of that price (2013 Patriots)?
We've seen in this offseason already that teams are highly unwilling to pay running backs closer to age 30, the supposed drop-off year in effectiveness for the position. In my research on these players, I discovered that while there is a drop in Total NEP for running backs after career Year 6 (most rookies come into the league around age 22), the sharpest decline on average is after career Year 3. We know that a running back's career is short, but this evidence seems to give a lot of weight to the idea that you need to rely on younger backs to be effective, all these factors serving to make it more imperative to hit on a running back through the draft or undrafted free agency.
When looking at the careers of these drafted runners, I plotted out their career Total Net Expected Points (NEP) to show me just how valuable each was for his team. Total NEP is a metric that shows us the number of points a running back adds for his team both on the ground and through the air. You can read more about NEP in our glossary.
I put that data side-by-side with each player's round selected in, overall pick, and draft cost per the standard NFL draft evaluation chart, which assigns each draft pick a relative value from 3,000 points for first overall to 0 points for 250th Overall. Next, I measured the correlations between each of these draft factors and a player's career Total NEP or average Total NEP over their career. The strongest such mathematical relationship was between draft round and career Total NEP, and even that was the tiniest of margins above the range of a negligible correlation.
Mathematically, then, there is no way to say that draft position correlates to success for a running back. But perhaps there is some rough way to measure general success of a draft selection by round?
Much like I did with my wide receiver draft article, I figured out and set "replacement-level" and "elite" thresholds for running back production, based on Total NEP numbers from last year. Assuming about three running backs on each depth chart, I decided that replacement-level simply meant that a player was good enough to make an NFL roster, and determined the 100th-best back in the league to be replacement-level (0.00 Total NEP in 2013). For elite production, I set the threshold at the top 10 runner in the league in Total NEP production from 2013 (35.47 Total NEP). After setting these bars, it was time to see how our RB crop measured up by round.
My goal was to see the percentage of players in each round that even once reached these replacement and elite thresholds. As was expected, the general trajectory of this data shows that, as the rounds get later, the chances are worse. Over 97% of first-round backs eventually have at least one replacement level season, while only 45% of seventh-round runners make that mark. Similarly with the elite, nearly 36% of all first-rounders have had one season of elite production by Total NEP, but even by Round 5, that elite talent is gone. Non-Factor % is simply the percent of players drafted in that round that never made any NFL impact in terms of career Total NEP.
Yet this seems to clash with our correlation results from before. If there is no correlation between draft position and career performance for running backs, then how could there be this clear of a trend with round-by-round percentages? The difference is merely in measuring complete production (career Total NEP vs. draft slot) and production potential. Teams clearly have a better chance to select elite talent at this position in the higher rounds, as this table shows, but the correlation data reminds us that there is no guarantee that a high-round selection will outperform a middle-round one.
The Value Point
I also did a quick calculation of the average career Total NEP of running backs per round, and divided that by the average slot value (per the NFL value chart) spent on running backs in each round since 2000. This will provide a quick reference for maximizing draft value in relation to career production; essentially, if I can find a career rusher who will accumulate 80 Total NEP in Round 4 (Marion Barber III), then I'd prefer to draft him at that value instead of someone who will give me similar production in Round 1 (Larry Johnson).
The later a team spends a pick on a running back, the more draft value they are maximizing by doing so. In a different way of wording this, by not selecting a running back highly (especially with no true top-tier talents available), teams are investing draft capital into positions that will affect their team in more drastic ways. Adopting the strategy of drafting a back later allows them to spend the high value on passing implements and then still find a quality runner later.
If there was a point that the natural riskiness of wear-and-tear of the running back position, the maximization of draft value, the likelihood of panning out, and still finding elite upside all met, I believe that the data shows this to be either the second, third, or fourth rounds. In the second and third, Replacement % is still high, elite upside hasn't yet dropped off, and the Non-Factor % is negligible. If looking to simply make a value pick, general managers should look to the fourth. There is much less chance of finding an elite player, but Replacement % is still nearly 80%, the Non-Factor % minimal, and NEP per Slot Value of these players skyrockets.
So, what can we take away from this? On a general level, we have reaffirmed that high-round running backs tend to be the more talented players. Yet we have also discovered through correlation that these higher-drafted players have about as much likelihood of becoming mediocre as lower-drafted ones do of becoming great. And finally, we've discovered that teams that wait might find better bargains, to a point.
Does this mean there's no way to judge a running back in the draft, and the whole thing is a total crapshoot? No, but in a league and a sport where Arian Foster can be signed off the street and Ron Dayne is selected 11th overall, perhaps the NFL is right, and should continue to rethink the process of drafting running backs.