A Davis trade is workable but we'd have to give up at least 4 players.
For example:
http://www.espn.com/nba/tradeMachine?tradeId=yd4ozszm
Crowder, Smart, Brown, and Morris for Davis works in the trade checker. At least 3 1st round picks would probably also be added to that list if this ever became a real thing. Right now it's just fantasy GMing.
Yeah, the point is not really exclusive for Davis, it's any "superstar" that has a max contract.
Crowder, Smart, Brown and Morris plus draft picks could probably get you most superstars if/when they become availble.
It's a lot to give up, but there is a reason Danny has been stocking up on wings
I think one thing overlooked is the Celtics aren't really in a position to trade for an all-star anymore without giving up some really core pieces like Brown, Smart, or Tatum. Last 2 years when we were conserving cap space we had bloated contracts like Amir and Zeller, even Jerebko to an extent. With our cap space maxed out now we'd have to combine smaller contracts to key contributors like vjcsmoke points out.
That's why a lot of basketball followers wonder when the Celtics will go all-in, while in fact we already have. Just not in the way that's really impressing considering the amount of assets we had and have. The benefit from these (lack of) moves is that we can still hope that the future is even brighter with a good development of Rozier, Smart, Brown, Tatum, Zizic and the Nets '18 + Lakers '18 pick.
Nonetheless, the Celtics were one of the teams that looked to be in a position to have an opportunity to become very dangerous fast. That ship has sailed. Probably to the disappointment of general fans, who don't understand why they let that chance slip.
Myself, I'm perfectly fine with not going into that direction of making a huge trade that could backfire because you gave up too many assets. What I don't like is that we didn't fully commit to the future instead. By giving max contracts to non-superstars and stop hoarding assets by letting useful role players walk we're decreasing our ability to make a move for a superstar in the near future.