Cuban is on record as saying he won't trade Dirk. So he has to commit to surrounding him with talent to win another ring. The Mavs only have 38 million dollars of salary on the books assuming OJ Mayo declines his player option (4 mill) and tests free agency.
So my question is this, who says no to Pierce, Garnett and Terry for the 13th pick and Shawn Marion.
Dallas isn't going to be a contender adding the 13th pick. Dallas is probably fourth on Dwight Howard's list and Josh Smith doesn't really fit along side Dirk. They add these three Celtics to play alongside Dirk and they are suddenly a very experienced playoff team, that has proven they have a shooters chance at beating anyone.
The Celtics add the 13th pick to go with the 16th and become about 4 million under the cap and have a 9 million dollar expiring contract in Marion, who is added to make this trade salary cap valid. Also, don't take the PR hit of trading Pierce to say New Orleans.
KG could also say no, but I think this is a trade he signs off on.
P.S. Knowing Danny I'm sure he'd try and make an O.J. Mayo sign & trade out of this,