Peyton Manning isn't the top quarterback in numberFire's fantasy football projections for the 2014 season.

You might think that's crazy, out of line, perhaps even impossible. After all, Manning just finished the most productive season for a quarterback in league history, and didn't show any signs of slowing down.

But that's not exactly how it works. There's a lot more that goes into ranking and projecting fantasy football than simply looking at last season and copying and pasting over similar outcomes. So what will limit Manning, and why did he fail to earn the top spot on our quarterback projections?

It's certainly not because he wasn't incredible last season. Since 2000, no quarterback has even come close to the Passing Next Expected Points production posted by Manning in 2013, and among the four players within 50 points was Manning himself in 2004. He's arguably the best quarterback over the past 15 years, and has two of the five most productive seasons to show for it.

A History Lesson

But there are factors working against Manning's quest to repeat his 2013 dominance for 2014 fantasy players. Since 2000, 12 quarterbacks have posted a combined 24 seasons of 300 or more fantasy points. Only two players have posted three consecutive seasons at that total: Drew Brees and Aaron Rodgers.

This statistic proves that these players are working in rarified fantasy football air, and even the slightest stumble would produce great, but not elite, fantasy production. So what is it about Manning specifically that sees him fall out of the top spot in our projections? Let's start with the reality of touchdowns from the quarterback position.

Since the dawn of the NFL, there have been only 26 instances where a quarterback threw 35 or more passing scores in a season, and no quarterback has accomplished the feat more than three times. This means that Tom Brady, along with Manning, Brees and Rodgers, have spent more than half of their careers throwing fewer than 35 touchdowns in a season, despite all of their record-setting efforts.

And all of them have been accomplishing these feats at an age closer to the typical athletic prime. Manning is 38 years old, with the added physical strain of a severe neck injury to deal with, and there's historical significance to this age bracket. Rich Gannon and Steve Young are the only other players to have a 300-point fantasy season at age 37 or older, while 15 of the 24 passers to post a 300 point season in NFL history were 30 years or younger.

In fact, when we narrow the bar a bit and look at only 200+ point seasons, we find that only six players have accomplished this fantasy feat at age 38 or older from the quarterback position. That's the age that Manning will be this season, and there has never been a 300 point performance from a quarterback that far along in life. Brett Favre's 2009 season in Minnesota comes closest, with only he and Warren Moon coming within 50 points of a 300 point effort at 38 or older. Certainly quarterbacks who get to that point in their career and are still seeing significant snaps are of a different breed, but to ignore age in the Manning formula may not be the smartest thing to do.

There's no reason to believe that Manning won't be productive, because he's the sort of special talent that Young and Favre and Moon were. But it's the level of production that we have to consider, and the statistics prove that older quarterbacks simply don't have a track record of sustained success, and the ages of 37 and 38 are usually a cliff for fantasy production. And while we're still projecting Manning to post 345 fantasy points, we have to always keep the things that can go wrong for fantasy players in mind.

It's not all just about age, either. Over the past six seasons, Drew Brees - our top-ranked quarterback - has netted a median Passing Net Expected Points score of 171.91 (which is absurd). Manning, not even counting his missed season, has a median Passing NEP of 162.50. Brees has been more consistent given Manning's arguable 2013 outlier, and that's important if you're snagging a quarterback early in fantasy football.

Manning's Fantasy Flaws

There are a couple of specific elements to Manning's game that should give cause for concern when compared to his closest competitors, Brees and Rodgers. First of all, Manning is completely immobile. In fact, of the 24 quarterbacks since 2000 to post a 300-point year, he is one of only two to do it without a rushing touchdown (Matt Stafford is the other), and the only one to ever do it with a negative rushing yardage total (a feat he accomplished last year).

More than half of that list of recent fantasy football successes at quarterback ran for 150 or more yards and three or more touchdowns, with Brees being the only consistent producer to fail to regularly pick up a good amount of fantasy points on the ground.

This is because standard scoring in fantasy leagues is inherently broken to allow for quarterbacks to pile up rushing yards and touchdowns at a better per-instance clip than passing statistics, while still producing passing statistics at a high volume due to the nature of their position.

What this also means is that Manning doesn't have any other leg to stand on. Once his arm is done, it's done, and there's nothing left for him to do but appear in Papa John's ads or save the Tennessee Football program from itself. Unlike Gannon and Young, who were still scrambling around at their old ages, Manning will be obsolete once his arm can't spin the ball accurately anymore, a state he's fast approaching based on the history of the position.

Oh, and there are outside influences at work here, too. Eric Decker has left Denver, robbing Manning of one of the most consistent receivers in the NFL over the past two years, and a great red zone threat. Decker was 11th in the league in Reception NEP in 2013, and is one of only eight wideouts to post back-to-back 100-plus Reception NEP seasons in 2012 and 2013.

Combine this with Drew Brees being the pinnacle of quarterback consistency (even more than Manning and at a younger age), and Aaron Rodgers providing a rushing threat that gives him tremendous upside, and it's fair to see why Peyton doesn't top our fantasy football projections.

It's not doomsday for Manning, as he's still projected to have an incredible season and be well worth your pick (if you choose to spend a premium pick on a quarterback). But don't expect a repeat of 2013, and don't forget about how great Brees and Rodgers have been. Consider this article as a splash of water on your blazing expectations for Manning, rather than a full-fledged extinguishing of his future.