Although the Celtics stood relatively pat at last month's trade deadline, the team very nearly agreed to a blockbuster deal that would have sent Paul Pierce to Dallas, according to Adrian Wojnarowski of Yahoo! Sports. Wojnarowski reports that the Celtics, Mavericks, and Hawks discussed a three-way trade that would have seen Boston acquire Josh Smith. However, the Hawks wanted a first-round pick in the deal, which the C's were unwilling to include.
According to Wojnarowski, the package that would have gone to the Hawks from the Mavericks featured Dahntay Jones, Jae Crowder, and Brandan Wright, along with the ability to swap picks in the 2013 draft. Based on Wojnarowski's report, it appears Atlanta was on board with the pieces coming from Dallas, but required one more sweetener from Boston, and the C's didn't relent.
The failed deal makes sense from Atlanta's perspective, since the club was looking to acquire some combination of young talent, expiring contracts, and draft picks in exchange for Smith. From the Celtics' perspective, Danny Ainge presumably felt that Smith was a player in his prime that the team could attempt to re-sign and keep for the long-term, though the GM wasn't willing to pay an exorbitant price to land him.
As for the Mavericks, they would have received another All-Star caliber veteran to pair with Dirk Nowitzki, but both players are in their mid-30s, and keeping Pierce next season would have eaten up the majority of the club's 2013/14 cap space. I feel like there must be a detail missing from the package that would have gone to Atlanta, since the Jones/Crowder/Wright trio earns significantly less than Pierce this season, meaning more salary would have to be included to make the deal work under CBA rules. Perhaps Shawn Marion, who has a $9.07MM player option for '13/14, was also in the proposal, which would have allowed Dallas to retain some financial flexibility in the summer. That's just my speculation though. Including Chris Kaman's expiring contract would also have worked for salary-matching purposes.
After being unable to finalize this deal, all three involved teams made smaller moves. The Celtics acquired Jordan Crawford from the Wizards, the Hawks acquired Jeremy Tyler from the Warriors, and the Mavericks and Hawks swapped Jones and Anthony Morrow.