What will this player's role be as a Chief?
Running back. Duh. He'll be providing depth at running back behind Jamaal Charles and Peyton Hillis. His role is pretty clear cut in year one -- depth at running back. He's also an insurance option should Charles not return completely healthy. He is not considered a 20-carries-a-game type of player.
Will the role change from year one to year two?
Possibly. Right now he looks like the third option at running back. But Hillis is on a one-year contract so depending on his future it's possible that Gray moves into the No. 2 role behind Charles.
How many downs can he be expected to play?
That's tough to tell right now but probably just two downs. He's not a strong pass blocker so I'm not sure how he figures in on passing downs. He's a strong runner who, sorta like Thomas Jones, could be slotted for a role as a guy who gets the short yardages.
Which current player on the roster will he beat out?
Shaun Draugh and Nate Eachus. They're both competing for the third running back role behind Charles and Hillis. Gray probably has the best chance of all those guys to make the roster.
What's his value on special teams?
To be determined but I think he does have a role on special teams. The Chiefs are filled up at punt and kick returner.
Does he have positional
Not really. His role is fairly obvious -- he's a complementary running back. He's not going to shoulder the load and he's not going to line up anywhere but the backfield. He doesn't offer much positional versatility.