He has looked fine on the field because he's played for 5 or 10 minutes . . . not an entire game. Those that have seen him in person have commented that he's not as fast, not as crisp, and has not had the same elusiveness as in the past (at least not yet).
We shall see if he can get seperation, yards after the catch, and take the pounding over and over again week after week. IMO, the Pats will not subject him to that on 100% of the plays. I suspect they will limit his snaps early in the year. They have a lot more receiving options than last year (Tate, Edeleman when he's not hurt, Gronk, Hernandez) so they will not have to rush Welker into the front line and will not have to force feed him the ball.
27th is probably a little low, but I wouldn't rank him where he was just yet.