History tends to be an interesting thing.

For Fantasy Football Calculator's average draft position data and is the fourth running back in My Fantasy League average draft position. As cognizant fantasy footballers know, age is a hotly debated and often discussed topic when it comes to drafting running backs. Now entering his age-30 season and with 2,279 career touches to his name, shouldn't we be a little more concerned about Peterson's downside risk in re-draft leagues this year?

The Dreaded Running Back Age Drop-Off

We can certainly learn from history.

Since the turn of the century, 18 different running backs have toted the ball at least 200 times in their age-30 season. This 30-year-old list of backs includes all-time fantasy football greats: Using these 18 30-year-old backs who saw at least 200 carries in their season as a baseline, I created an average season of rushing and receiving output to form some realistic expectations for what we can expect from an aging (30-year-old) running back.

Why the 200-carry cut off? (It wasn't arbitrary.) In his career, Peterson has never seen fewer than 208 carries in a single season. If we assume Peterson even misses a few games this year for a margin of error, he has averaged 19.8 carries per-game in his career -- meaning the 200-carry cutoff is likely his absolute floor in 2015.

Clearly these numbers in the above table are nothing to stick your nose up at. Running backs in their age-30 season are more than capable of putting up solid fantasy numbers -- but is this historical average actually worthy of top-five fantasy pick? Remember Peterson is currently a top-four running back in early fantasy drafts.

For added context, the 30-year-old season average of 221.6 PPR fantasy points would have been good enough for the following running back finishes over the past five years: RB10, RB16, RB13, RB14, RB14. We can assume that while those finishes are definitely solid -- especially given the wear and tear at the position -- that the historical average (221.6 fantasy points) is nowhere near worth a first-round fantasy pick.

Taking it one step further, only two (11.1%) of these 18 running backs in the sample have finished as a top-three running back in their age-30 season (June Average Draft Position. All of these backs haven't played in every single game over the past five years and some were drafted post-2010, which is denoted below. Also included is each back's per-game fantasy output over their past applicable seasons.

The data is sorted by "RB1%" which is the number of weeks a running back finished inside of the top-12 PPR running backs divided by total games played for the years spanned. All scoring is point per reception (PPR).

Just by this pure output-based analysis alone, Adrian Peterson has been a rock-solid force in his games played finishing as a "RB1" (top-12) in 51.7% of weeks -- yet he still doesn't even have near the weekly consistency Arian Foster has possessed over the past five seasons.

Speaking of which, Arian Foster is a year and five months younger than Peterson, has 661 fewer career touches, and has averaged 2.4 more PPR fantasy points per-game over the past five years. Foster is going 13 picks after Peterson in re-draft leagues right now. Oh.

Of course Peterson did miss 15 games last year which could have boosted his numbers overall, but this analysis doesn't exactly paint a rosy picture for Peterson's top-four running back average draft position.

Jamaal Charles has boasted a slightly higher floor over the past five seasons, finishing as an "RB1" 56.3% of weeks over the past five years. Matt Forte and Peterson have the exact same PPR output per-game. Plus, Forte has missed five games in his last five seasons. Peterson has missed seven (not including 2014). Additionally, Marshawn Lynch has finished as a RB1 45.8% of the time when discounting his 2010 season where he spent four games in Buffalo and then was traded to Seattle.

Even take LeSean McCoy for example. He's no longer a Philadelphia Eagle and Buffalo's less efficient offense may cap his ceiling and floor this year and in seasons to come, but he has finished as a PPR "RB1" (top-12) more often (56.8% RB1%) and has averaged a marginal 0.1 fewer fantasy point per game than Adrian Peterson has over the past five seasons.

Is Adrian Peterson head and shoulders above these fellow top running backs? That's a tough argument to make.

The "Fresh Legs" Theory and Rebuttals

The drafters taking Peterson in the top-four typically state one of the following two narratives. First, it's "Peterson has fresh legs" after missing 15 games last season and having an almost full calendar year away from football. But is this a good thing? How do we know if it's a net positive that Peterson hasn't carried a football on an NFL stage in almost a year? Plus, it's not like his 2,279 career touches are just expunged from his record.

Peterson will be a case study in whether or not it's beneficial for a running back to have non-injury related time off during a career. Is that a type of risk worth taking with your first round pick this year? That's also a tough argument to make.

Next, the following narrative surrounds itself in an improving Vikings offense commanded by second year quarterback, Teddy Bridgewater. Minnesota has also added an element they didn't have last year with Mike Wallace's speed and ability to take the top off of defenses. It's fair to speculate that this will be one of the best -- if not the best -- offenses Peterson has ever been on, talent-wise.

But just last year, the Vikings offense finished 25th in schedule-adjusted Net Expected Points (NEP). Peterson's presence plus Bridgewater's progression could help propel the offense forward -- but let's not pretend that Minnesota was some offensive juggernaut last season.

Realistic Expectations

To be transparent here, I am not saying Adrian Peterson will be a bust in fantasy football this year. He could very well have a solid season and once again re-assert himself as one of the league's best runners. Our projections peg him as the fourth-best fantasy running back for the season. But keep in mind, history isn't exactly in favor of aging runners and Peterson hasn't even been the lone, dominant fantasy back some have made him out to be.

So, Adrian Peterson will look to add to his on-field legacy in his age-30 season in 2015. He has a year's rest under his belt, but that's a shaky, narrative-based foundation to build your fantasy team on. If Peterson does defy history and re-pay his average draft position, he'll do so facing long odds this season.

Fairly, Peterson is a solid fantasy option this year in and up-and-coming offense -- but there are multitudes of risk that are not priced into his value in 2015.