A LOT.

Drafting them waaay too high, too low, or not drafting them at all, when a different decision would be better.

It's among the toughest positions in football to project well, judging from NFL history. How many first rounders have been busts? How many really good backs have been drafted late? And the Rams found Lacy and Cunningham after the draft, and both men gave them excellent production when they had a chance.

It's not a science, despite all the analytics. Too many other factors can screw all of that up . . . from injuries, to personal tragedies, to bad, good or indifferent coaches, staff, schemes, etc. etc.

The stars have to align just right in most cases. Sometimes, of course, a runner is just sooo dang good, he can overcome pretty much anything.

But that's rare.

Just a hunch. But Kelly's going to be very productive for the Rams.