There's a trend in fantasy football to jump on second- and third-year players who might be ready to take the proverbial jump. There are plenty of examples of this happening. Marion Barber jumped from five TDs as a rookie to 14 in his second season. Frank Gore had 1,087 more rushing yards from Year One to Year Two. Steven Jackson, once he was out of Marshall Faulk's shadow, took jumps in both his second and third seasons, vaulting to fantasy superstardom.

But don't get too excited about certain guys just because they are young. After all, Maurice Jones-Drew, as highly as he's regarded, actually took a dip in his second season. Ronnie Brown saw only a modest jump in his second-year numbers and was hurt for much of his third season. And Reggie Bush — once perennially on the rise in terms of reputation — still hasn't lived up to his massive hype.

With that in mind, here are three backs you might want to be a little cautious with:

Titans RB Chris Johnson
I am still bullish about his chances to be a good back again in his second season, but beware of the injury factor. He's a 200-pound back who approached a 20-touch-per-game pace last season and might not hold up for an entire year again. The team had to spot his carries at times down the stretch in 2008, and I suspect they'll have to do it again. There also are rumbles out of Tennessee that perhaps Johnson has gotten on a bit too high of a horse, irritating some of the coaching staff. I also want to point out that his four best games last season came against some bad defenses: those of the Bengals, Chiefs, Lions and Browns. The Titans' schedule appears more stout this season, with only one opponent (St. Louis) ranking in the bottom quarter of the league in run defense from last season. After a rookie campaign in which he approached 1,500 total yards and scored 10 TDs, it wouldn't shock me to see him dip to the 1,000-1,100 range with six or seven scores, especially if he can play only 12-13 games.

Texans RB Steve Slaton
I admit I never saw this coming. I had major concerns about Slaton coming out of West Virginia, especially after I heard he bulked up prior to his rookie season. I feared he would lose his zip as a runner, but a funny thing happened: the second half of the season, he was more productive as he got more carries. That's hard not to like when you are reviewing his fantasy prospects in Year Two. But I suspect that the system, as much as anything, is a big reason why he was so successful. And I also worry, like I do about Johnson, that Slaton is an injury candidate. Plus, he developed a tiny fumbling habit late in the season with more work, which is always a concern. I still think we are talking about a successful back in Year Two with home-run potential (he had six 40-yard plays and gained a healthy 4.8 yards per carry). But I wonder if he doesn't level off a bit now that he'll be a major focus of opposing defenses.

Lions RB Kevin Smith
Yes, he's the starter and the Lions want to run the ball more often, control the clock and win games much the way Jim Schwartz's old Titans teams did for the better part of a decade. But Smith might not be an ideal fit in Detroit's offense. He was drafted by the previous regime because he fit the team's zone-blocking scheme, and with a man-blocking system in place Smith won't have the luxury of running those zone-stretch plays much anymore. With only Maurice Morris really any threat to take carries away from Smith, he still should be a productive back and it was nice to see him finish his rookie season so strongly. But he might not be a perfect fit in the new system, and the team could look to add another back that is after this season.

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