Jterrel hit the nail on the head. Any WR taken in any portion of the draft should be used as a 2 or 3. It's too tough of a position to adjust to right out of the gate.
Like QB, very few WRs have come out and made an immediate impact as a rookie.
I like the Reggie Wayne comparison. Like Wayne, Doucet came in with a lot of talk about his potential. Wayne was a very good WR at Miami (he actually broke a number of Irvin's records), but he was overshadowed by more talented players.....this is just like Doucet.
Doucet was a player that came in as a HS QB...he's spent the last few years trying to master the WR position. If anything, he'd be a solid return man.