By B.J. Rudell, special to

It happens every season, as predictably as Denver snow, Phoenix droughts and Los Angeles temperatures moving dramatically from the low-80s to the lower-mid-80s. It’s midseason in the NFL, and that quick-cutting, fleet-footed running back you drafted in the fourth round -- the one you knew would put you over the top against that nerd in the accounting department -- is about to lose his starting job. Why didn’t you see this coming sooner?

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A frighteningly high percentage of running backs who begin the year as starters end it as second- or third-stringers. The difference between fantasy success and failure hinges, in part, on your capacity to identify which tailbacks are not long for this fantasy world. Here are three players for whom you can still garner trade value. Get rid of them before they’re worthless.

Shonn Greene

Greene has a few things going against him. First and foremost, he’s a middling talent when compared to other starting running backs. He’s currently playing over his head with 5.6 yards per carry this season after entering the year owning a career 4.1 mark. A negligible role in the passing game limits his appeal. Additionally, his longest run in 919 NFL carries netted only 36 yards. Simply put, Greene is a half-decent running back who’s not good enough to make a meaningful fantasy impact more than once or twice a season.

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No doubt, if Greene played for the Eddie Lacy-less Packers or Matt Forte-less Bears, his value would be higher. The Titans were 20th in points scored last year and are 24th this season. A tailback with more quickness and open-field running ability might be a better fit. But Greene’s deficiencies don’t line up well with his team’s limitations.

And while free agent acquisition Dexter McCluster is nothing more than a role player, Bishop Sankey was supposed to give Greene stiff competition, but fell short during the preseason. Still, as the first running back taken in the 2014 draft, Sankey will be more than an occasional contributor; it’s simply taking a little longer than some expected.

The 29-year-old Greene is winding down his career with few scoring opportunities on a two-touchdown-per-game team. By midseason he’ll be taking a backseat to Sankey, making him unstartable in any fantasy league.

Toby Gerhart

Ranked No. 21 among running backs and No. 44 overall on the Top 300, Gerhart was another player I avoided on draft day. Most experts rated him among the top 20 at his position, touting him heavily as an RB2 and perennial fantasy starter. I’ve never bought into him, and neither should you.

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Principally, Gerhart is not an every-down back. He’s the B-movie actor who gets the attention of an A-list director, is cast in a $150 million film and then reminds everyone that acting is harder than it looks. Entering 2014, the 27-year-old spent his entire career in Minnesota as Adrian Peterson’s backup. Most touches occurred in garbage time and/or when the outcome was assured, leading to an impressive four-year mark of 4.73 yards per carry, including an improbable 7.9 yards per carry last season. Given his skill set, such numbers are unsustainable as a starter.

Also, Gerhart is probably the Jaguars’ slowest tailback. His running style might keep the chains moving on third and two, but not on first and 10. In other words, facing starting defensive units on 18-22 touches per game, he’ll continue to have difficulty breaking into the open field and racking up yards. Some insist he’s faster than people think. But in game action, I don’t see it. He's only averaged two yards a carry with no touchdowns, which is indicative of what's to come.

As for competition, Gerhart faces a group of younger (and arguably more talented) running backs vying for his starting gig. Chief among them is Denard Robinson, a more elusive runner with higher upside. Jordan Todman and Storm Johnson also could make a small-to-medium impact as the season progresses. Even if you believe Gerhart is better than all of them, for a guy who's never had more than 109 carries in a season, he’s a prime candidate to wear down and give way to one or more of his more able-bodied backups.

By midseason, Gerhart will be a 25-45 yards-per-game, change-of-pace running back with almost zero fantasy value.

Steven Jackson

It’s not just about age, although that’s an important factor. A 31-year-old rusher isn’t merely on the downside of his career; he’s at the end of it. Like a boy band member hitting puberty, the high notes are fewer and farther between. Personally, I want to see Jackson kick butt. Realistically, the Falcons will need more from their running game to be a playoff contender.

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Workload has also taken a toll. From 2006 to '10, the Rams ran Jackson into the ground to the tune of 298 carries (while averaging over 350 total touches) per year. He’s currently 20th on the NFL’s career rushing attempt list with 2,598. In that context, his injury-riddled 2013 season wasn’t surprising. It would be shocking if he reached this season’s midpoint unscathed.

At first glance, Jackson appears to be in control of his own destiny. Backup Jacquizz Rodgers’ career yards per carry is 3.7. The 28-year-old Antone Smith has only eight career rushing attempts. Neither guy poses any threat to Jackson’s playing time; nor would they belong in a fantasy starting lineup if Jackson were sidelined. The real competition in Atlanta comes from Devonta Freeman, who like several other rookie tailbacks has not made the immediate impact some expected. But an impressive preseason reinforces the notion that Freeman will challenge Jackson for touches before long, whether or not Jackson’s health holds up.

By midseason, Jackson will be either sidelined with a nagging injury or relegated to part-time duty alongside Freeman, keeping his upside to 60 total yards per contest and a touchdown every three or four games.

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