At some point there needs to be a breaking point. If you sit there and tell someone a deal is good (like it sounds the Nuggets did), then ask for more after Billy King goes out of his way to make it happen, then you're creating bad karma.
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Masai Ujiri needs to either stop negotiations until the deadline, or make the deal. But he needs to not second guess whether or not he's getting the best deal and have some confidence in himself, because the worst case scenario (which is very real) is that Carmelo, Billy King, and everyone is just sick of it and Melo takes the best deal the Knicks can offer him in the offseason, and the best that Denver ends up with is a trade exception.
I don't know what the Nuggets said about it and I still can't blame them for looking for more. There is no guarentee on draft picks or Favors and Melo is one of the best players in the league. I still think the GM should push for the best deal because all the pressure is on NJ to get Melo.
I think Melo gets moved and doesn't sign an extension where he goes at worst if New Jeersey doesn't get involved. Maybe Dallas scoops him up to make a run. But you could be right. I just don't think there is any chance New Jersey retracts their current deal, even if Denver pushes for more.
I think Denver trying to get the most for Anthony they can is admirable, but leading teams to think you've got a done deal, or at least one that won't change, then demand more, is very very stupid.
New Jersey is not in the worst position in the world either. They've got draft picks, they've got a player they love in favors, and they've got Devin Harris and Brook Lopez. The only player on their roster that will be there in 2 years that is over 25 is Devin Harris. If they wash their hands of Anthony and decide he's not worth blowing up their entire team, and that it is better to build through the draft, then Denver just lost out on the best haul they're going to get.
Also, if New Jersey drops out of this deal, then the other offers out there will drop, and Denver's position will become significantly weaker.
You say the pressure is on New Jersey, but if you beleive that the package around Favors, Harris, and a couple of draft picks is the best deal out there, then they're fundamentally bidding against themselves if they add in Billups or Harrington.