Youth can be both a blessing and a problem in the NFL. It’s also a necessity, which makes balancing talent and age a difficult act rooted in risk assessment.

In Buffalo, general manager Buddy Nix is going through that process. But for the Bills it’s a little different, and a little more complex.

Their decision involves an extension for a running back’s contract that’s set to expire a year from now, a running back who’s on the wrong side of 30. It’s a decision that’s already been made, and from a short-term financial perspective Nix’s pledge earlier today to extend Fred Jackson’s contract for at least one more season and maybe several is one of the easiest calls he’ll make all offeason.

It would be that easy, and the discussion would end there if this was purely about the Benjamins, and the Bills’ coffers were the only area effected by a decision to keep Jackson around until at least the end of the 2013 season. His expiring contract is a four-year deal signed in 2009 worth $7.5 million, so after his production and age are weighted evenly, we’re guessing a one- or two-year extension would likely be worth somewhere in the neighborhood of $3 million. For the price Nix is paying, he’d be getting Pro Bowl value for a minimal investment.

But if money was the only item up for debate in any contract situation, then we’d have many more people qualified to fill GM positions around the league that are oddly still vacant.

When his season ended early and abruptly in Week 11 after he fractured his left fibula, Jackson was easily on pace for a Pro Bowl season. He was playing his 10th game of the year when he went down in late November against Miami. Although it’s admittedly difficult to trust a pace that’s projected over six games and nearly half a season, Jackson’s 934 rushing yards on 5.5 yards per carry through just those 10 games meant he was running towards 1,494 yards, which would have easily put him in second place overall in league rushing behind Maurice Jones-Drew.

So he’s worth the money, and he’s worth the commitment. Jackson will turn 31 in 10 days, which would typically put him one year beyond the running back rocking chair age. But he’s not a normal running back, because he received his first +200 carry season at the age of 28. Jackson’s career path is similar to Thomas Jones’, and he’s running through unique running back territory. Even this year he wasn’t on pace for 300 carries (272), so it’s not absurd to imagine Jackson still being productive as he approaches 35.

And that’s great for the Bills, but maybe not so great for C.J. Spiller. Selected at the lofty position of ninth overall in the 2010 draft, Spiller plays one of the few positions where being highly productive as a starter right away as a rookie is feasible and frequent. But he’ll enter his third season with that role still either fully or mostly in the hands of another running back. That situation has emerged because of Jackson’s success, but also due to the lack of pounding that’s made his success possible at an advanced age.

When Spiller was drafted, Jackson had 425 career carries through 40 games, and now through 30 games Spiller has 181, a difference that’s quite small with their six-year age gap. Spiller has an abundance of speed, and the ability to shift and make tacklers miss in the open field, and it’s those skills that led to 641 combined rushing and receiving yards, and five touchdowns over the six games after Jackson’s injury.

But as I wrote back in September, the presence of Jackson is limiting Spiller’s ability to contribute during his prime years, possibly and likely leading to a wasted pick for Buffalo at a position where marquee running backs are often found well beyond the first round, and even after the draft among the undrafted free agents. That was already a legitimate concern this season, and it’s one that will grow when Jackson’s extension is signed. It’s just a matter of how much it grows.

When Jackson’s current deal expires, Spiller will be set to celebrate his 26th birthday in August, just prior to the 2013 season. If we assume the maximum length of Jackson’s extension is two years, Spiller will then be 28 by the time he’s given a chance to be the primary runner.

There’s more, though, because there’s always more. Spiller’s contract will be expiring at the same time in that scenario, and the Bills would be left with one fading runner, and another who’s two years removed from the age of 30, and still hasn’t carried a backfield on his shoulders for a full season.

That’s a fine scenario if Spiller was an undrafted diamond found in several mounds of rough, which is the case with Jackson. But with this extension, Nicks will be taking a nice return on one investment, and trading it for a potentially poor return on a top ten first-round pick.