Most pronosticators have size going up and down this draft with SGs and SFs falling. If there is a run on centers and PFs the end of the draft might see some very interesting wings dropping into the Celtics lap. Brandon Rush, Nicolas Batum, Chris Douglas-Roberts, Bill Walker, or Courtney Lee could all fall if the bigs go where they aren't projected to go. it is amazing how many GMs still draft size over skill in the middle and late part of the first round.
The other thing that might occur is that someone may fall out of favor and land in their laps. One of Hibbert, Robin Lopez, DeAndre Jordan, or Joe Alexander could fall much further than expected and be there for the taking.