Sean Spence is my prediction. I think he's going to start game 1 and I think he's going to add some much needed speed and athleticism to the middle. Yeah he'll make some mistakes, but his recovery time is so great that he'll get in position better than Farrior has the past few seasons even when he takes an initial bad step.
I also think DeCastro will be a quality starter from day one.
And I think Chris Rainey is going to be a special teams demon. And will probably add more and more to the offense as the season goes on.
I think Adams will be starting by November's end.
In other words I think this is an exciting crop of rookies and I think they'll add more on field value to the Steelers this year than any rookie crop in recent memory.