It's always tough to gauge incoming rookies especially in terms of your fantasy draft. This year you will not see any QBs having any kind of impact for any team ,and it is also hard to imagine any WR standing out (there definitely is not a Calvin Johnson type in this past year's draft).
While WRs seem to have the easiest transition and most productive rookie seasons, look for the best fantasy rookie to be among the RBs.
Darren McFadden by rank leads this group of rookie runners, but will he be the most productive this season? He is certainly the most talented, but is he any every down back? Or will he suffer from the same growing pains that Reggie Bush is still figuring out—how to make the smooth transition from college to the pros.
With that being said I feel as though many people will hype up McFadden as they envision him as being comparable to last year's rookie sensation, Adrian Peterson. I highly doubt McFadden will near the stats AP enjoyed in his first full season, but you will see Run DMC selected way earlier than he probably should be (and thus the first rookie RB taken in most drafts).
Plus, the Raiders seem set on handing over most of the RB duties to Justin Fargas, who impressed the coaches last year when he emerged as the every day RB over Lamont Jordan and Dominic Rhodes. So, McFadden will have to show why he deserves to steal carries from the already established Fargas.
While I still know McFadden is more than capable of having an electrifying impact his first year, I see others having more initial success than him.
I view Jonathan Stewart as a late round steal. He was in fact a late round steal in the actual NFL draft, and can also slip to your fantasy team in the ladder rounds of your own draft. He is a very physical runner who dominated defenses, especially his last season in college playing for the Ducks of Oregon. He had a toe injury that led to his falling draft status but the Panthers are optimistic all things will be a go for their rookie RB once the season rolls around.
With the departure of DeShaun Foster, the only competition for Stewart will be DeAngelo Williams. Williams has struggled in his own right in his attempt to gain starter's status. He has been dubbed a change of pace back, and hasn't really progressed as much as Carolina had hoped he would. If Stewart can beat out Williams for the bulk of the carries, he will be a legit number two RB in all formats, especially since he will get most of the calls around the goal line.
Other Rookie runners that you may want to take a flier on include Matt Forte of the Bears and Kevin Smith of the Lions.
The Bears are fresh off their divorce with troubled RB Cedric Benson and always have been a team that stresses the run. They recently signed Kevin Jones, but his health status is still up in the air, and the Chicago coaching staff has already been impressed with Forte's overall game.
Kevin Smith also finds himself in a favorable situation. Smith was an absolute workhorse in college for UCF and he could be the back of the future for the Lions. His only competition right now is Tatum Bell.
If Tatum Bell is your only main threat at playing time then Kevin Smith is sitting pretty. Bell has failed to finish a full season as a starter for the Broncos and Lions in consecutive seasons, so don't count on him holding off Smith for long, if at all.
Rashard Mendenhall is also a nice handcuff for Willie Parker owners, as he will likely get the bulk of goal line carries. If Willie Parker gets injured like last year, Mendenhall will turn into a stud.