The average career of an NFL running back is the shortest in all of football.
Remember Matt Forte's 2009 season? Yuck. Have you seen Forte in 2010? Wow.
In fantasy football, the RB position is perhaps the trickiest in the game. Other than the top dogs, many players border on the fence of relevancy for the majority of the season.
While it usually takes an injury or a benching for most backups to make a significant impact, that's not always the case. Sometimes, a simple changing of the guard can really ignite an offense.
Fantasy owners should take note of the following five guys who could really amass some big time value as the season rolls on.
Make sure you don't hit the snooze.
Green-Ellis, or "the law firm", as he prefers to be called, really proved capable of handling the load in the New England backfield.
With coaching staff favorite Kevin Faulk sidelined for the season with a torn ACL, Green-Ellis' emergence from the backfield speaks volumes of the lack of depth at the position for the Patriots.
With just banged-up veteran Fred Taylor, seldom used Sammy Morris, and newcomer Danny Woodhead to compete for carries, Green-Ellis has a chance to have legitimate fantasy value the rest of the way.
He certainly won't rack up many (if any) big-yardage games, but he's a definite threat to sniff the end zone in almost every matchup thanks to a potent offensive attack.
Kuhn looks like to be the biggest beneficiary from the season-ending injury sustained by starter Ryan Grant.
After a failed experiment with Brandon Jackson acting as the lead runner, the Packers are going to look to keep Kuhn involved in the offense as an integral piece of the ground game.
Slated to be the team's starting fullback entering the season, Kuhn's head-down style of running between the tackles has some people remembering ESPN anchor Chris Berman's favorite NFL player: Mike Alstott.
With the Packers unlikely to make a move until just before the deadline (if they make one at all), Kuhn deserves to be rostered in most leagues, especially with a tasty matchup against Detroit on the slate for week 4.
While his workload will be somewhat unpredictable, the Packers offense seems to be in the red zone quite frequently these days.
Even though he looks a little rusty, Lynch has put up some impressive numbers over the last two contests.
After looking like he was destined toward a somewhat lost season, Lynch has established himself as the most productive option out of the team's options at the position for the time being.
While his increased playing time is more likely motivated by the team's desire to trade him rather than actually play him, if he continues to play this well there will certainly be a team (GB?) that comes calling.
He's not recommended as an immediate pick-up and has a long way to go toward belonging in starting lineups, but Lynch is certainly on the right path.
And if he does find a new home? Watch out.
Ryan Torain experienced the most success of his career in Denver under Mike Shanahan, so why should their tenure together in Washington be any different?
With rumors running rampant that current starter Clinton Portis will soon be headed for a third-down role, Torain's role on offense is set to increase dramatically on a weekly basis.
Looking as healthy as ever after battling injuries over the last couple of seasons, Torain's fantasy relevance is very real and is worth an immediate add in all leagues.
A Shanahan favorite, Torain should not be counted on to start until we see a slightly larger sample size, but all signs are pointing way up for the young man.
Snelling has proved time and time again that should Michael Turner fall victim to injury, he's more than an adequate fill-in.
When Turner went down after week one, all his backup managed to do was rush for 129 yards and two scores. Additionally, he managed to haul in five passes for 57 yards. Just another normal day.
Even with Turner's return last week, Snelling still managed to get 14 carries and made the most of it with 62 yards (4.4 YPC). "The Burner" is about as fragile as they come, and it seems that he's always got some sort of injury nagging him throughout the season, making Snelling just a carry away from being a huge fantasy factor.
One of those rare backups who could start for a lot of teams, No. 44's powerful running style causes a lot of problems to opposing defenses and could wind up being the best waiver wire pickup this season.
Ethan Norof is a writing intern for Bleacher Report, follow him on Twitter.