The top four running backs in the upcoming NFL draft have something in common — none of them plays in a traditional pro-style running game.

At Arkansas, Darren McFadden and Felix Jones were used in a system that utilized both halfbacks together frequently. McFadden would sometimes take a direct snap and either hand off or run himself.

Rashard Mendenhall was used in the option at Illinois, and he rarely ran behind a fullback.

Oregon ran a similar offense with Jonathan Stewart, spreading the field and attacking the edges of the defense with the running game.

So for NFL teams, evaluating these prospects is slightly more difficult than evaluating running backs like Adrian Peterson, for example. Peterson played in a more traditional offense at Oklahoma, running between the tackles more frequently.

The margin for error in evaluations always increases when projections are involved, and there is some projection involved with McFadden, Jones, Mendenhall and Stewart.

"It does cause some problems," one AFC general manager said. "They're running sideways a lot, not playing downhill as much as they will in the NFL."

Colts President Bill Polian points out running backs in such systems eventually do everything NFL teams are looking for them to do — they just don't do them as frequently as some other backs.

So for scouts, it might mean more work.

"You have to watch a little more tape with these guys," the general manager said. "You might see them run from an I formation with a fullback five times a game instead of 25 times, so you have fewer opportunities to see how well he does what you're looking for."