When you're the fantasy owner of a stud running back, life is good. When they're the back that leads the league in carries, rushing yards and/or touchdowns, it's even better.
What isn't good, however, is when you're the fantasy owner the next year that drafts that same stud runner and the guy blows his knee out. But he didn't just blow his knee out. He killed your entire fantasy season, as well.
Think back to 1998, when Jamal Anderson crushed the NFL en route to leading the Falcons to the Super Bowl. He paced the entire league with an insane (and then record) 410 rushing attempts. Those totes led to an insane 1,846 yards and 16 touchdowns.
Unfortunately, Anderson blew out his knee right away in 1999, and totaled just 59 yards and no scores off of 19 carries.
He wasn't an aberration. He's probably where fantasy researchers really started thinking twice about drafting the previous season's carry machine.
Since Anderson, nine running backs who led the league in rushing attempts (and usually yardage) dropped off considerably the following year. Most of them because of injury, because they were literally worn down.
Names like Shaun Alexander, Curtis Martin, Larry Johnson, Eddie George, Stephen Davis, Jamal Lewis, Michael Turner, and even Chris Johnson get the tears flowing.
They all sound like fantasy busts now, but before they killed your fantasy hopes, they were crushing it by toting the rock well over 300+ times.
But this is a trend we can't ignore.
Last year's top carry guy was Maurice Jones-Drew, and with knee problems over the past two years, he has to be a clear bust candidate.
With all of this in mind, here's a quick look at five other backs (other than MJD) that for whatever reason, may not live up to expectations in 2012:
1) Marshawn Lynch - Seattle Seahawks
Lynch went into Beast Mode and likely worked his way into a lot of drafts' first rounds with 1,204 rushing yards and 12 touchdowns. His final stats were good, but it was his consistency that caught everyone's attention (at least one score in 11 straight games). He carried the ball 285 times last year and just got a new deal.
He's still a solid fantasy back that could do even better in 2012, but he could also disappoint - especially if you draft him too early.
2) Frank Gore - San Francisco 49ers
Gore appears to be out to show he's still elite, but there have already been whispers about him scaling back his workload. Perhaps he should listen.

Gore finished 2011 with 282 carries for 1,211 yards and eight touchdowns, but like usual, he ran into some injury troubles. Gore had solid season numbers and at one point was one of the hottest backs in the league last year. However, from weeks 10-17, he scored just three touchdowns and never topped 90 rushing yards in a single game during that stretch.
A key note is that 2011 was just the second time in his career he has played in all 16 games.
3) Steven Jackson - St. Louis Rams
Jackson didn't carry the ball all that much (260 attempts), but he once again played with injuries and operated behind a weak offensive line. This guy takes so many hits and is routinely bogged down by some kind of ailment.

He'll be 29 in July and eventually he's going to break down. This year could be perfect timing, as the Rams drafted rookie running back Isaiah Pead to help take some of the load off - and eventually replace Jackson.
4) Darren McFadden - Oakland Raiders
Michael Bush is gone, which means McFadden is finally slated to get all of the carries in Oakland's rushing attack. Unfortunately, it's hard to trust that he'll be on the field to actually get them.

There's no doubting McFadden's talent and potential. He showed us all in 2010 that he's the real deal when he piled up 1,157 rushing yards and seven scores in just 13 games. But it's what happened in 2011 that is troubling.
McFadden went down in week seven with a foot injury after a very solid start, but never returned. In all, McFadden has missed 19 games to start his career, and is a major injury risk.
5) Michael Turner - Atlanta Falcons
This whole topic started with the idea that if a guy is run into the ground the year before, he may break down the following season. MJD got that conversation going, and the other four guys above are more "risks" that guys that took a major beating the year before.

But we're ending with a carry machine that is holding a big red flag in Turner.
Not only has Turner already endured the curse we mentioned earlier from 2008-2009, but he's now carried the ball 635 times in the past two years.
He has already visibly been slowing down and is now in his age 30 season. There couldn't be a better time for him to hit that wall for good.
While he's still a productive back, guys that carry the ball that much and take so many hits have to be major risks heading into the new year.
Combine carries and a spotty injury history, and it's only a matter of time before all the guys mentioned in this article start fading away. It may not happen to all of them in 2012, but you should be weary of them and draft accordingly, or at least try to get the risky options a round or two later than everyone else.
Disagree about some of these guys being risks in 2012? Comment below!