Straight forward answer: Michael Porter. If there is any team who is picking at the top of the draft that can afford to bring a prospect like Porter along slowly to ensure full recovery, it's Boston. His ceiling is essentially Kevin Durant. Think Tatum with a couple extra inches. He is an incredibly fluid athlete.
The Danny Ainge Answer- from my persoective, there are 7 elite talents in tbe draft. Picking at 4, there will absolutely be a team that sees one of the "TOP 3" (ayton, bagley, doncic) or whoever is available at 4 (portee, bamba, young, sexton) as a top-two or top overall pick in your average draft. I think Danny is aware of this, and he will try yet again to do a small trade-back to remain in that top 7, but also gain anothee future asset to dangle at a team like New Orleans.
It is clearly DA's draft philosophy to make these type of moves, and any player not named Ayton or Bagley in this draft is realistically not starting for this team as constructed for a couple seasons.