Legarrette's Blount's biggest weakness was not knowing the assignments last season. At times, that was his strength too, as it allowed to turn nothing into something. But over the long haul, running backs will gain more yards when they know their assignments and follow their blocking. Blount did not show the ability to do that - and he again failed to do so against the Chiefs. That's a problem.
Being a good running back is more than just the ability to run and make people miss, it means understanding plays, knowing where the play is supposed to go, having the patience to let blocks develop and trust your blocking, and the vision to cut back and go outside the boundaries of the play when needed. On the very first play from scrimmage against the Chiefs, Blount failed to do that, and it's a great example of why he needs to improve. Hit the jump to see the footage.
Knowing where to hit the hole is part science and part art, and it's not always clear. What is clear here, though, is that Blount does entirely the wrong thing. This is easily seen when you pay attention to the fullback, Rendrick Taylor, who is leading the way. Taylor hits the man on the end of the line of scrimmage, and stands him up. If Blount trusts his blocking here, he can cut upfield before he gets to Taylor, where the linemen and tight ends have the defensive linemen blocked off. He could even cut it all the way back on this play.
The one thing he can't do is run past the block by the fullback, because that brings the blocked defender back into play. Instead, Blount does exactly that, and he almost gets tackled by the defender, only miraculously avoiding a loss on the play.
If you look at the play develop, you can see everyone on the left side of the line winning their blocks, and all defenders flow to the right side of the offensive line. If Blount had trusted his fullback and his blocking, he would have gained at least five yards and would have had a solid chance to break a very long run. The way he ran the play he did gain five yards - but that was the absolute best-case scenario, and a tackle for a loss was much more likely.
Of course, it would have been possible that Blount was told to simply keep going outside - except that toward the end of the play, we clearly hear one of the coaches scream "HE MISSED HIS CUT!"
Blount is already a good and productive running back. But he can be so much better if he just stops missing his cuts.