Well, that's one way to spruce up the running game. I don't know that there's a back in the league worth a first-round pick, but if there is one, it's probably one with a top-five pick pedigree that's still on his rookie deal.
(Ed. note. The last running back drafted in the top 10 to not finish his second season with his drafting team was Lawrence Phillips. The Rams released him. Richardson's quite a bit better of a player.)