[QUOTE=JB1089;4503219]3 skill sets for a running back: running, receiving, blocking[/QUOTE]
Can't forget about vision, durability, awareness, strength and toughness.
I've enjoyed and loved watched all-time greats such as Barry, Smith and Tomlinson over the years, but Adrian Peterson is the ultimate back. The greatest mixture of size, speed and power that I've ever seen. Also has great field vision and is one of the toughest RB's that's ever lived to play the game. He's fearless.