How Much Does Draft Age Matter for Running Backs? – The Wrong Read, No. 30

Welcome to the 30th installment of the “The Wrong Read,” an article series that reflects on recent podcast episodes, pushing the ideas discussed on the podcasts to their logical conclusions and offering some further thoughts on the topics broached by the guests and hosts. Given all the players who’ve changed teams lately, it might be worthwhile to revisit how those players should be expected to perform. Here’s what I wrote about WRs who change teams.

The issue of whether a player’s draft age influences his chances for success at the NFL level has come up on a few RotoViz podcasts. In previous articles, I explored the importance of draft age, or a player’s age during his rookie season, for both wide receivers and tight ends. In both cases I found that draft age is extremely important—that WRs and TEs who play as 21-year-old rookies drastically outperform their older peers. Is this also the case for running backs? That’s what the article you’re reading will try to determine. A future article will do the same for quarterbacks.

We know that draft age is important for WRs and TEs. Let’s quickly review exactly what that means and how we determined this. Looking at every player-season since 2000, I calculated each player’s draft age his age on December 31 of the year he was drafted, or basically the end of his rookie season. Then I compared the fantasy production for each age group. Results from the previous two studies were even more striking than I could have imagined. Rookies who play WR or TE at the age of 21 have historically produced more top-ranked seasons with more average fantasy points than any other group—and it’s not even close. Now let’s apply the same methods to the RB position to see if this trend holds.

Draft Age and Career Production

First, average fantasy points:

The difference between 21-year-old rookie RBs and 22-year-old rookie RBs is not as great as at the TE position, but it is still significant. RBs who play their rookie seasons at the age of 21 go on to average nearly 150 PPR points per season over the course of their careers. RBs who play at age 22 average just over 90 PPR points, and as we move up in age we move down in average points, for the most part.

If we look at the percentage of RB player-seasons that have ranked in the top 24 by draft age, the results are pretty similar, but the differences between the top age groups and the rest are greater:

Almost 40 percent of the seasons produced by RBs who were 21-year-old rookies are RB2 seasons. RBs who played their rookie season at age 22 produce a top-24 season just over 20 percent of the time. RBs who were 23 or older combined for only about 40 percent of the top-24 RB seasons, despite accounting for two-thirds of all RB player-seasons.

Here’s another perspective on the same data. The following chart shows the share of total RB seasons and top-24 RB seasons that each age group has accounted for:

Although 23-year-old rookies account for the highest share of all RB seasons, it’s actually 22-year old rookies who account for the highest share of top-24 RB seasons. However, relative to their share of total RB seasons, 21-year-old rookies outperform the most. Consider this: 21-year-old rookies account for nearly as large a share of top-24 RB seasons as 22-year-old rookies do of total RB seasons. 21-year-old rookie RBs have gone on to account for almost as large a share of RB2 seasons as 23-year-old rookies, despite the fact that 23-year-old rookies have played almost five times as many total seasons.

Controlling for Outperformers

Some of the best RBs ever, including Marshall Faulk, Edgerrin James, Steven Jackson, and Emmitt Smith, were 21-year-old rookies. This is of course significant—these are the exact types of players we’re hoping to discover when evaluating NFL prospects. But it also skews the results of the tables above, because these RBs were so good for so many years. What if we just want to know the chances that a RB in a particular age group will produce a top-24 season at least once in his career? The following chart answers just this question:

There have been 57 RBs who played their rookie seasons at the age of 21 and also played at least one NFL season since 2000. Of those players, 28 of them, or nearly half, have produced at least one RB2 season since 2000. By comparison, only about 29 percent of RBs who were 22-year-old rookies have historically produced at least one top-24 season.

The 2018 Rookies and a Few Arbitrage Possibilities

The 2018 class of RBs is notable for its depth and top-end talent. But it also should be notable because many of the top prospects in the class will still be 21 at the end of their rookie seasons. All of the following RB prospects will play the entirety of their rookie seasons at age 21:

Other players who were still 21 when their rookie seasons ended and have yet to produce a top-24 season include Marlon Mack and D’Onta Foreman, both of whom showed flashes of being promising NFL RBs in limited action last season. Compared to many of the top 2018 rookies, both can currently be had at a discount.