By Guest Contributor Scott Warfe

Finding topics for off-season discussion used to be rather simple. When the 49ers were bad, you could throw a dart at the roster and be assured that there was a reasonable argument for replacing the player hit. Now, it is complicated.

Frank Gore is a perfect example of such complexity. Statistically speaking, he had one of his better seasons. Sure, his YPC (4.3) was down from his career average (4.6), but it was still up from 2010 (4.2). What’s more, though he was hampered by hip/knee/ankle/etc. injuries, he played in every game, a first time since 2006. He also had the second most rushes in his career with 282 (which is just 30 behind his career high from 2006). So, in all, Gore had a solid year.

Nevertheless, Gore’s position is listed near the top of free agent wish lists. The fear is that Gore is quickly nearing the end of his shelf life. And, as it were, there seems to be a simple equation to determine whether or not he is: (Age) + (Position) + (Carries) = Running Back Deterioration. Such a theorem, Gore’s dissenters claim, clearly suggests that Gore’s skills are due for a rapid deterioration.

Unfortunately, for Gore and his most ardent supporters, most studies confirm this.

Doug Drinen of Pro-Football Reference found that “the peak period for running backs is age 27-28. As a group, running backs under 27 tend to improve, and running backs over 27 tend to decline.”

Drinen, in a different article, develops an equation that would not only confirm his findings, but also “predict the future career length of a back given his level of quality and his previous workload:”

Future rushes =~ 3203 – 104*age + 2.3*VBDLastYr + .813*PreviousVBD – .13*PreviousRsh

If the formula is right, then Gore has approximately 415 more career carries, or two more years before complete futility.

This timeline is in accordance with what Tristan H. Cockcroft (an unfortunate name) of ESPN has found. Cockcroft believes his research is definitive, noting he has “rarely seen a theory in sports that has stronger statistical evidence than this one: NFL running backs hit a wall once they turn 30. Nay, they hit a concrete wall, and it practically stops them flat.”

A quick glance at recent history lends further credence to Drinen’s and Cockcroft’s respective theories.

Shaun Alexander saw a precipitous decline in productivity after eclipsing 28 years of age. In fact, in his proceeding seasons, Alexander never again reached the 1,000 yard mark.

LaDanian Tomlinson would only surpass 1,000 yards once after his 28th birthday. Same with Jerome Bettis, Marshall Faulk, Edgerrin James, Eric Dickerson, and OJ Simpson.

But still age notwithstanding, there is reason to be hopeful about Gore. Of the running backs listed, Gore has the fewest total carries (through age 28):

Age notwithstanding, it would appear as though Gore still has some life in him.

Yes, Gore was hampered by injuries last year. Yes, he is likely slower. Yes, he is older. And, yes, his shelf life for Running Backs is ending sooner-than-later. But, for the most part, Gore has always been hampered by injury, and he’s always lacked speed. And yet, these two seemingly inauspicious traits have never impeded his ability to be an effective Running Back.

That said, a study by Haverford University’s Chase Kennedy suggests that the 2012 season will predict Gore’s effectiveness as a runner for the next three to four seasons. Kennedy found that upon reaching 1750 carries, “production shows its largest expected decline,” but that the “trend does not continue when running back’s reach 2000 carries.” In other words, if a Running Back reaches 2000 carries, their decline levels off.

In essence, Kennedy found that for some, the decline is merely a slight regression, not a complete demise, as with Alexander. This holds true for Emmitt Smith, who would surpass 1750 carries in 1995. After that season, Smith’s decline was sharp:

But, in the following seasons (when Smith would surpass 2,000 carries) his production remained stable:

The sharp decline seen in 1996 is not continued in proceeding seasons. James’ and Tomlison’s numbers show similar results: once the running back reaches 2000 yard plateau, that running back’s skills will remain relatively stable.

And so, Gore’s inevitable decline next year will be a clear indicator of the type of back he will be for the proceeding two years of his contract, which would roughly equate to 500 carries. That is, once 1,750 has been surpassed, the next 500 will either look like Alexander’s or James’.

Still, it would be short-sighted if the 49ers did not pursue a running back this off-season, if only to lessen Gore’s load while also diversifying the offensive. However, doing so should not break the bank. While Peyton Hillis and Marshawn Lynch are attractive options, their cost would likely be too prohibitive. Click here to see who the 49ers will most likely pursue in free agency.

In addition to blogging on Posttraumaticsportsdisorder.com, Scott has been featured onOregonSportsNews.comSickoftheRadio.com, and Examiner.com. Follow him on Twitter@ScottWarfe.