Problem is Beane seems to have a WR X type that is just not that productive in the league. The big, physical jump ball guy, rather than the fast, quick, wins with separation guy. Coleman is the former and there was literally no doubts about his weaknesses at the draft. It was all over his college tape and showed in his rookie year. He can't get open, except on slants and flats. He doesnt' have the physical traits nor the route running expertise. Now, he could develop the latter still, but he has an uphill battle given the lack of physical traits.
Many scouts pegged him as a heavy slot, so its not surprising to see he did best in slants.
The only reasons he was productive at all as a rook, was Josh. He dimed him on back shoulder throws and scramble plays. Keon will never be a #1, but he could be a solid contributor and dawg. Hope he learns to play special teams, so he can take on more of the Mad Mack role