Age Adjustment: Running Backs

There is one single, inescapable and unstoppable constant in life: Time. In this sport, where fresh young talent constantly replenishes the player pool, the margin of error for veterans is minuscule. The aches and pains accumulate over the years. As soon as a player misses a practice or loses a step, his career is in jeopardy.


Time is the critical component of dynasty football that owners must learn to master. In dynasty, every owner races against the clock to gain the most value out of each of their players. The opportunity of youth must always be balanced against the reliability of experience. Every player is a ticking time bomb and owners can't afford to hold the hot potato too long.


Time's universal nature allows us to build potent universal stats. This first installation in our Age Adjustment series will focus on Time's most vulnerable prey, the running back.

Obligatory picture of Father Time


As the new college crop enters the league, the total number of running backs increases at each age until age 25 where the decline begins. RBs start getting replaced before the end of their first contract (most enter at age 22/3). From there, the rate of retirement is steady and merciless, growing year after year.


Our data covers 25 years of football. We averaged the total number across 25 seasons to give us an approximation of how many RBs of each age we can expect each season. A major cliff is noticed after age 30; across the entire league, there's only about 6 RBs over age 30 that make it onto a roster each season.


The NFL doesn't care how many Pro Bowls you made or Super Bowls you've won, they will throw you out at the first sign of slowing.


Rate of Retirement


The high rate of retirement reflects league perceptions about carrying an older back. Older players carry higher injury risk, theoretically decreased performance, and are less valuable from an investment standpoint as they take away important developmental opportunities for younger players.


Interestingly enough, our evaluation of pure injury risk (measured in % games missed) did not show a significant discrepancy between older and younger RBs. Even at an older age, RBs over age 30 were able to play as many games in a season as the younger backs were. The main difference was that there were simply less older RBs making it onto teams. There was, however, a significant difference in the fantasy success rate of these older backs and the decline is easy to see below.


Success Rates

Asking whether this declining success rate is related to actual decreasing efficiency of the older RB or due to the decreasing opportunity they receive is irrelevant to us. We are not the ones deciding how many carries Frank Gore gets. What matters is that older RBs do not have fantasy relevant seasons at the same rate as the younger RBs. Observing the chart above, we find that there will be one 30 year old each season that will produce an RB2 performance on average. From a pure probability standpoint, we can see that an older player has a lower rate of success than a player still on his second NFL contract.


The probability of RB success reaches a peak with the age 28 cohort. From there, the downhill roll begins as teams stop investing in older players, and instead, turn to the youth found in draft. Both the raw total of older backs and their success rates drop like a rock. Over the last 25 years, there have only been 8 times that an RB over the age of 30 has had an RB1 season.

We see the same pattern when we use raw average PPG and its deviation.

This data is telling the story of the life cycle of the running back market. At age 21 we see the highly talented Junior RBs declare early and enter the league to produce at a high success rate. From age 22-24 we see the other less talented RBs enter the pool and the average drops. As these younger RBs enter their second contract, the success rate rises as the talent is sifted from ages 25-32. Although the retirement rate begins to gain significant momentum at age 28, the actual performance of the RBs that do survive endures a bit longer. The lag between RB extinction and RB performance may provide an interesting key to unlocking value in backs toward the end of their life cycle.

The Age Adjustment Model


The astute dynasty owner values his players the way the NFL does. As a player ages, his value sinks. Eventually he will succumb to the hand of Time and be laid to rest with his football forefathers. To account for that natural decay, I've built an Age Adjuster. The initial use for Age Adjustment is to objectify how a player's value changes throughout his career. Using this model, we'll be able to capture a player's value within the context of Time. This is the next step in the evolution of dynasty football.


Each age will score a certain percentage of points that will add or subtract from a parameter in question. The Age Adjustment model uses a combination Retirement Rate, Success Rate and Average Points. Each position will get its own unique model, the RB Age Modifier will be the first installation.



Because the Age Adjuster is built on percentage points, it has universal flexibility to modify any stat. It's value is two-fold: the Youth Bonus it provides will help identify breakout stars, and the Decay Decrement will help identify when a player's value is about to run out.

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